Holiday Bazar: Tracking a TrickBot-Related Ransomware Incident

Holiday Bazar: Tracking a TrickBot-Related Ransomware Incident

On 21 December 2020, the start of the Christmas week, evidence emerged of a ransomware campaign leveraging BazarLoader (also referred to as KEGTAP) and linked to the TrickBot ransomware gang. Initially disclosed in a tweet, the campaign rapidly unfolded over the course of that day.

Based on discussions with intelligence partners and various network defenders, the adversaries responsible for this activity appeared to rapidly move from initial infection at victim locations to interactive operations en route to attempted ransomware deployment. In previous operations, TrickBot activity is associated with the deployment of Ryuk ransomware. At the time of this writing, DomainTools researchers were unable to confirm a final-stage payload for this specific campaign.

Although this specific campaign has since passed, it contains many lessons for network defenders and Cyber Threat Intelligence (CTI) professionals for monitoring and analyzing emerging campaigns to enable dynamic, flexible defense.

Initial Delivery and Download Vector

Analysis of the campaign indicates initial delivery takes place using a legitimate third-party email messaging or notification service. In this specific case, the adversary leveraged GreatResponse, used for email marketing and landing page design, to deliver seemingly benign-looking email messages with “Corporate Document” or similar themes. Observed link examples include the following:

 When accessed, a victim would see a landing page such as the following:

The link would direct to a Portable Executable (PE) file, discussed in further detail below, hosted on Google Drive. Further execution would require the user to run the downloaded executable for follow-on exploitation to occur.

The above activity is consistent with observed TrickBot operations—as well as other entity tactics—using third-party services to evade detection and mitigation. For example, TrickBot gang campaigns have previously used third-party delivery services such as Sendgrid to distribute initial phishing messages. Follow-on payloads have also been hosted on cloud file storage sites, such as Google Drive, as well.

Examining Droppers and Installers

Further activity requires not only user interaction with the phishing message (displaying the landing page link) and downloading the file hosted from Google Drive, but then executing the payload as well. 

Overall, as part of the completion of this “kill chain,” DomainTools researchers observed 18 samples of the next-stage payload. Naming conventions for these files matched the landing page themes, although DomainTools researchers expect more variants likely exist beyond our visibility.

SHA256 MD5 File Name
90a51557f3438fec9b2ffab5828751cb43fa9eeb1fa84468effe95a9f13f12d0 774bdb15ae6c7dedea62ebf0985a3451 Corp_Document.exe
74d757a4cabf26009ab5f1064939c54ceea43a8399419a7c965b2edb7e0ed648 2d8c8177ab8dddb90a42ea03827eeb37 Company_Doc.exe
0e809ef68d85e730190db2663ab914dfd6ccb4c355a051841366b3a5c91ada63 0dd55da99e569959b4a338c5ef67e2b4 Corp_pdf.exe
2be628add2ab1be6120026893c6a7a51dc0b3f81c7421349504a6010581aa427 a54c10b1372f0dcc492d78349d7d2ad4 Corp_Document.exe
21df8a331f272ed9b6b72509028af31612292c9f3c0776a4472b2b585c142648 eeb42010fcbabf4079994a831637105f Company_Doc.exe
82dbcaa7694a6e763300cee1d4b2ef6e65f6a65fd93663365ce032823984cb21 7ef4f4eb66ea52a0f1471169e2a53758 Corp_Document.exe
2c6b49185dea80c48dcdd1c316a0de3413ff52a67819a720419c630093b5e638 1cd5e8bbd17c4764f9db10529bd25608 Company_Doc.exe
3941242436e943fbfb7b1767aa2615bcc5637da3d939d3b06a1572de8bf044a1 5af82b394bae65462bfb643933c09930 Doc_21.12.exe
4c4b00621d0e57bcdf188174a539ca3c92a4fc96647eabe6d79c17ae04bd519d f0cc16198bdf3ef628264794bf074817 Corp_pdf.exe
3985648d781de545cf1209469454b88f7f6e54696b6a050dbb7ba2ba1eae2cec c3ad311ea64ad7981b6451f47ff88202 Corp_Document.exe
436301cb89dadecb6c6cefc043b8a4d8f47de2054b1e84e1612cf061cd14dc15 977a7762afdecc0b1989b5f5451b7c6b Company_Doc.exe
44075e5eb7ee76b006a8f4cf2bfee30dec3c5007c02f8657f956429bb976ea4b d52710baa7cc837a628a5ef1c5cdfd92 Doc_21.12.exe
bed288ad6037546ecfb9e912518583fefbb7685681a8ecfd5b27502735de20bd b0c831758a9726010f13058e37c7c2c5 Corp_Document.exe
102dca8d268dbbba33770459009d4d67e0d714b44523c28fce57ee83fe186a31 e018926f81bf4599dedb4ae1696689b1 Corp_pdf.exe
bbe896ab541c703d699f97311a30c2e07be98be1ebf7eed9a9a1fd7dfa2efb5b de65816eca59774ffc2fa96cebcb68c8 N/A
69aa97d3507d4ccf7dc0bd0a97cfe509edfbdf16734fcc40cd01d8dd659fd450 4c52e80e6bb5452f42600ee7bb5c4ee7 View Report.exe
392c73ffa3b1513cd8de9435d7e76320eff7f98db884eb6bc776c3b2bea7c77e eea12082de2cbb26af85b4060c4baa34 Corp_Document.exe
e1841e78c6dace694cc5172bac1068b9ede38a3623c5429a877eb1190d90a14d bd7d9ae98ec2adf3c9e545b9567a4b8c Company_Doc.exe

One sample, “View Report.exe”, is a 32bit executable that appears to date from late November 2020 and from part of an earlier, undocumented campaign. The remaining samples are 64bit executables compiled on the day of the campaign, 21 December 2020. 

The executables in this campaign are signed with the same Sectigo code signing certificate, with the name “СКАРАБЕЙ” (Russian for “Scarab”) and a fingerprint value of “348F7E395C77E29C1E17EF9D9BD24481657C7AE7.” This certificate has since been revoked by the issuer.

While signed binaries are not new to ransomware or related operations (with notable signed examples including but not exclusive to Ryuk and LockerGoga variants), they continue to pose a threat to users as many applications and security products inherently trust code-signed items.

Following successful binary execution (through user interaction), the malware attempts to resolve and connect to one of at most two Command and Control (C2) servers embedded within the binary. Successful connectivity allows for further actions on target, including the attacker taking control of implants to launch further commands or move laterally within the victim environment.

Associated Network Infrastructure

As noted in the original Tweet sparking this investigation, there were several domains immediately identified as associated with this campaign. Further investigation and analysis of samples yielded additional items, shown in the following table:

Domain Registrar Create Date IP Hosting Provider SSL Certificate Hash
birch-psychology[.]com NAMECHEAP INC 12/10/2020 192.236.155.212 Hostwinds LLC. 2929ea338eb1a9aeb83aa8dcf0814812505995b8
busybjjj[.]com NAMECHEAP INC 12/10/2020 195.123.241.79 ITL-Bulgaria Ltd. 5a8da3e012eee5505a04e09a1e323acbb1c14b86
flourish-psychology[.]net NAMECHEAP INC 12/10/2020 192.119.171.165 Madgenius b93e985da0cc7d540c4ebddf9136dbf948e7522a
flux-psychology[.]com NAMECHEAP INC 12/10/2020 107.152.32.121 ServerCheap INC 4ee5e1eaaab74ccb04010b735b75d5b3b98a29b8
freekaratee[.]com NAMECHEAP INC 12/10/2020 94.140.114.152 SIA Nano IT dbd1959d1a0575219f265ed48bfe71ca422549bd
impactpsychcoloradoo[.]com NAMECHEAP INC 12/10/2020 185.82.127.115 SIA Nano IT 2852cb1c32b90554e5fd2b6b8e494c45d1e66e83
livingyoga-denver[.]com NAMECHEAP INC 12/10/2020 138.201.113.2 Hetzner Online AG 52b825408a1cb843e84d623e6506c29e807e1bd9
ustfitf[.]com NAMECHEAP INC 12/10/2020 195.123.240.192 ITL-Bulgaria Ltd. e5add3d65ebeba577d383657148f92fd53f337f3

The identified network infrastructure serves as the next stage of the intrusion. Following malware installation, active C2 would be used to further exploitation of the victim, leading to likely ransomware activity.

Pivoting and Identifying Additional Items

At this stage, we as defenders are largely in a “reactive” state with respect to identifying indicators and characteristics of this BazarLoader campaign. While quickly ingesting and deploying defensive measures based on indicators and observables may represent an improvement over completely passive defense, it still leaves much to be desired.

Instead, by identifying characteristics inherent to the campaign—both its network infrastructure and malware samples—we can both gain greater knowledge of the attacker’s tendencies while enabling defense attuned to these tendencies. For the latter, this means adapting defense to the adversary’s fundamental behaviors as opposed to chasing specific examples of those behaviors as represented by indicators.

Network Observables

Looking at the domains identified above, several “themes” emerge:

As previously documented by DomainTools, these observations can be used to unearth additional C2 infrastructure for threat hunting or preemptive defensive purposes. Unfortunately, at first glance by plotting the above items using DomainTools Iris visualizations, there seems little in common on a technical level to enable successful pivoting to additional infrastructure.

Yet a combination of limited technical details that overlap (registrar, TLD use, and time of creation) along with “thematic” observables (the naming conventions used) can enable us to unearth additional items.

With this hypothesis in mind, looking for items with a similar technical structure that also mirror the “local service” or “local business” theme, we can identify the following through DomainTools Iris:

Domain Create Date IP ISP SSL Certificate Hash
app-space-cleaner[.]com 12/15/2020 46.4.76.174 Hetzner Online AG d456b68598481ca23f7736828731c3730d641192
babynameinspirations[.]com 12/14/2020 135.181.154.50 Hetzner Online AG N/A
bbdworld[.]net 12/18/2020 195.201.9.204 Hetzner Online AG N/A
blacksockproductionss[.]com 12/10/2020 192.119.162.84 Madgenius N/A
blueridgecabin-cleaning[.]com 11/13/2020 94.140.115.253 SIA Nano IT 5392b3c24963f7de3c3f7e0711d4f6eba4f0f31a
carwashevanstoon[.]com 12/15/2020 94.140.114.54 SIA Nano IT a856e01b468b46f4316ef026bf74351ce27647c5
cguschool[.]com 12/9/2020 116.203.253.24 Hetzner Online AG N/A
cleaningcompany-online[.]com 12/1/2020 192.227.231.237 Virtual Machine Solutions LLC 1eab0efacfeb82bde18db1200ff03bb0526ac60d
coloradobudokann[.]com 12/10/2020 195.123.233.78 ITL-Bulgaria Ltd. N/A
crowleycollegeprepp[.]com 12/10/2020 107.152.42.146 ServerCheap INC N/A
data1-posten[.]com 12/7/2020 168.119.171.234 Hetzner Online AG 30f46401c6abd0c9a629c64259592b5c6ca974a6
familyzstore[.]com 12/11/2020 198.54.117.244 Namecheap Inc. N/A
first-posten[.]com 12/7/2020 168.119.171.234 Hetzner Online AG N/A
form-feedback[.]com 12/7/2020 178.63.220.179 Hetzner Online AG 23f3a3a27edcb956c33aa57c71abced34e6c454c
greatsfamily[.]com 12/9/2020 198.54.117.244 Namecheap Inc. N/A
injektorrx[.]com 11/13/2020 94.140.114.187 SIA Nano IT 0aec5a4f8860b44d77fb47f053e391c83aa36cfb
inmanheatingandcoollng[.]com 12/15/2020 94.140.114.135 SIA Nano IT 66688b898713f2d840985325d093e46e5fbbc0e6
intlupdate[.]com 12/8/2020 5.34.178.204 ITL LLC 35d8a65cba2c02c4dcc7bb7e00680ae5c4aa4823
johnnyclean-carwash[.]com 12/1/2020 192.119.171.231 Madgenius a24abeb13e6ad93f9c82af26352d33a358c9c634
johnnykashjewelsapp[.]com 12/15/2020 195.123.237.139 ITL-Bulgaria Ltd. N/A
jordanbelforthiring[.]com 12/16/2020 192.64.119.2 Namecheap Inc. N/A
kizienservices[.]com 12/9/2020 195.201.179.80 HostMaster Corp N/A
lovelyhomemart[.]com 12/7/2020 176.9.29.52 Hetzner Online AG 9b48c3e61c1aa79155b725f5fd4f47bc755d0d2d
manageupdaternetwork[.]com 12/17/2020 94.140.114.160 SIA Nano IT N/A
my-space-cleaner[.]com 12/10/2020 46.4.76.174 Hetzner Online AG b613424256682a4a4d4465a8b84741e4055f211b
newappday[.]net 12/9/2020 95.217.229.116 Hetzner Online GmbH N/A
niftythriftsteals[.]com 12/13/2020 49.12.15.63 Hetzner Online AG 630a232a25964fbdb8031ecfd5860c7578210222
nord-city[.]com 12/11/2020 46.4.70.54 Hetzner Online AG 179e434d8e2b4c6190037f55bf94c1c766e58777
open-register[.]com 12/16/2020 198.54.117.197 Namecheap Inc. N/A
posten-order[.]com 12/7/2020 168.119.171.234 Hetzner Online AG a6c19e7d55629da02919432bd5e92bd8395715e7
pulsehomeowner[.]com 12/14/2020 159.69.186.9 Hetzner Online AG N/A
qureshisgym[.]com 12/20/2020 95.216.159.168 Hetzner Online GmbH N/A
real-posten[.]com 12/9/2020 135.181.94.39 Hetzner Online AG N/A
rentinginnovations[.]com 12/13/2020 159.69.186.9 Hetzner Online AG N/A
rmflaging[.]com 12/10/2020 94.140.115.145 SIA Nano IT N/A
service-masterss[.]com 11/13/2020 141.136.0.3 SIA Nano IT N/A
speed-posten[.]com 12/11/2020 135.181.94.39 Hetzner Online AG N/A
stonyhand-carwash[.]com 12/15/2020 138.201.112.173 Hetzner Online AG N/A
tracking-posten[.]com 12/7/2020 168.119.171.234 Hetzner Online AG b62aed1d366c54148617c3c30f6883b0a92c4aa6
trak-no-posten[.]com 12/10/2020 135.181.94.39 Hetzner Online AG N/A
trakaing-pass-posten[.]com 12/9/2020 168.119.171.234 Hetzner Online AG 1fac7b2ae6b7ea5b7c032c9cd1f06db9844a6a72
washguystxx[.]com 12/4/2020 141.136.0.25 SIA Nano IT N/A
worldnewsfeed[.]net 12/15/2020 88.99.102.85 Hetzner Online AG f852a683482e9fbab0044e0257eee159e0bdf044

This list is extensive and includes items that are likely not related to this campaign, but other items seem to fit the pattern observed quite well. Examples include:

These items form the basis for further threat hunting and CTI analysis. Given that all of the identified items are marked as likely malicious based on DomainTools risk scoring algorithms, the options available to defenders range from adding the domains and related infrastructure to blocklists as a preventative measure to monitoring them for further activity. For example, items such as those called out above could be flagged in various services, such as DomainTools domain monitoring, to identify when changes or file associations occur.

File Patterns

In addition to domain patterns, the malware samples associated with this campaign also feature several commonalities that can be used for either hunting or alerting purposes, depending on the tools and visibility available to the researcher. From the information available thus far, we have the following insights:

From the above, DomainTools researchers began investigating multiple data sources for similar file characteristics as well as items contacting domains revealed in the network pivoting exercise documented in the previous section. From this and follow-on analysis from initial findings, DomainTools researchers unearthed another BazarLoader campaign from 17-18 December 2020. The following samples and C2 domains were observed:

SHA256 MD5 File Name C2
b455c245254ebf9691dcf7f02323b42c5b34998a440fa1b8a0f981f0ce3e2bfb f1672efcf0685d933fe104e1c4639a64 N/A johnnyclean-carwash[.]com
c9a66cff4c5b5d74545c1eabc9da4ecf618f9c72174150569daa58e843cee5e5 c28b472f5162a4a58d29aed1f1b2fe06 BonusReport.exe johnnyclean-carwash[.]com, akbuilding-services[.]com
a7738dddb62919658c1fe3d339ccae6d0d2afe85a1bccccfce6f8a9ee6b4c5de 356bc937d6e70bbc75ed7a3c47a2f184 AnnualDoc.exe cleaningcompany-online[.]com
0d848d9675e6e6d12d1d158b07b636db246e02145beb5db7ae9be36cb5e1c3ff 872608fe080163292505b2bc5e8880c0 AnnualDoc.exe johnnyclean-carwash[.]com
68ed893ae6ab2d7f00c3aacf46bc0c92966b647bcfe7e940a5d3ee55af01105a 3ec43f75ab39833054610e3e6f0cb217 AnnualDoc.exe johnnyclean-carwash[.]com
c67c3cc34905f4751e2f48363a0cf3cf69799f020687b6f5852058d3abd1c31d a13275cb285c392c9ddc765d0f5f0754 BonusReport.exe johnnyclean-carwash[.]com
7978e198f7523d487e13a742101810d765c4ed191920d571ea51c99cc18eb795 8763f3f259a7f7fb8e9e91cd3d6491c7 N/A johnnyclean-carwash[.]com
d33a8c70a8ae4f8eeb2f3708820486c0248edf340120f6380a8a3540e212a5dc 946c9c2574feaca8d674914faeeca65a BonusReport.exe johnnyclean-carwash[.]com
9b29924a22ef01cb9c3b8c98d5cc4508836427335d3949c93e7a4c50c2bd40d5 9014ee7a206b40f1cf81de0918ff8c9f AnnualReport.exe cleaningcompany-online[.]com, akbuilding-services[.]com
75a52886c5a83dd25cb7e7d393320ee439f7605dbe41818057fc34c1102bbfc1 b8648e857b5e80920bd08a749b3d57ba AnnualDoc.exe cleaningcompany-online[.]com
bcccb14658e8c1bee8107a2c314957c2bd9e505e73012b0aaa18df9fedf99248 dd0c5c4d2cdf6f57be6c7f4d7e64f5fd AnnualReport.exe johnnyclean-carwash[.]com, maidtoorderfll[.]com
56c5bee33c17a453c900725f88efb0466fd928072c420955fa599b518b9dfcd2 ee85e8c0956d2021732d9606120401f9 AnnualReport.exe cleaningcompany-online[.]com, akbuilding-services[.]com
898f6e91c82bf23b5b95e0560292b1c610970b3062eeeb9980c75f954e5024a9 2946562b29462362faf215bf7a2fcaa6 BonusReport.exe johnnyclean-carwash[.]com
7ed66b0d81958d709b7f3067f9bdc69c25cbb955506c4a812cf0b6b9a7590f0d 949099803fcee51754b88ad6d121fb46 AnnualDoc.exe johnnyclean-carwash[.]com
a32ed4b36d44c489341721920d27294cab78ad7bd970c8ac6baa3edc4337a600 5686d8ae3dbaf2898116583c91adf368 BonusReport.exe homeclean-heroes[.]com
288d28f4d53d8e44d599a4d2f70b53d5b13f0827ad2b7a953a7a3cbd6e67bf25 dfa0bc9da86deb5f9419d96d5dc60a64 N/A johnnyclean-carwash[.]com
ac696ef5a12039b72e408b6b14e08823c407ee652a6a36b7c33d01cd8d373497 67c2474a2fb201491c0ff5ff7ab783ea AnnualReport.exe johnnyclean-carwash[.]com, akbuilding-servicex[.]com
30b2922c78a07dcd65a6f93886e7efcd6c3c883c70c2dc5f37cf41e50f240903 f7079cd6f7bb70b8a341af27c62be1aa AnnualReport.exe johnnyclean-carwash[.]com

Multiple samples were identified with C2 infrastructure linked to the domain pivoting in the previous section. While this did not appear to succeed in identifying “new” items (as the files in question appear to have been active from 17-18 December 2020, before the originating campaign sparking this investigation), their discovery indicates other items in the list of possible domains may relate to future campaigns by the same actor. Additionally, some items were revealed which featured C2 domains not related to the pivoting documented earlier. Examples include:

 

Although exhibiting C2 domains beyond initial research, the items were linked by a common code signing certificate (again from Sectigo, and since revoked by the issuer) with the name “ИНТЕЛЛИТ” (Belorussian for “Intelligence”) and thumbprint “1103DEBCB1E48F7DDA9CEC4211C0A7A9C1764252”:

Although a different certificate than that used in the 21 December campaign, it reflects similar themes and observations. One item in common with both signing certificates is the prefix “OOO”, which in Russian (and related) languages is equivalent to “Ltd.” While there are many legitimate entities that can and do sign their software with certificates including “OOO” in their name, this may function as a robust indicator for organizations with few or no commercial ties to Russian or related language entities for blocking or filtering files with code signing certificates containing such language. This code signing observation represents a start in overall defensive planning against malware campaigns such as that observed in this report.

Defensive Recommendations and Mitigations

We have already discussed several examples of possible alerting items for this campaign, ranging from signing certificate observables to infrastructure commonalities. However, network defenders must be attuned and responsive to a variety of adversary “tells” in campaigns to ensure robust and complete defense from intruder operations.

First, the simple identification of new or anomalous network traffic—whether as email links, user interactions, or programmatic communication—can do wonders for network security posture. For example, all of the domains identified in the analysis so far have scored as likely malicious through the DomainTools risk-scoring algorithm. By programmatically tying network security monitoring or log capture (such as proxy logs) to a threat intelligence source such as DomainTools, defenders can rapidly identify communication to new, likely risky sources and use this as a mechanism to launch further investigations. Done in a timely fashion, this can work to disrupt ransomware actor operations and interrupt events before they proceed toward ransomware deployment.

Second, organizations must be attuned to the malicious use of code signing for the delivery of malware. In this specific campaign, the Sectigo signing authority was abused to sign malware for delivery and execution. From a defender’s perspective, we cannot completely distrust Sectigo (as it is used by many organizations), but we can identify ways to narrow our degrees of trust to reduce attack surface. Within the context of the currently discussed campaigns, identifying the “OOO” string, corresponding to “Ltd” in Russian and related languages, may be sufficient to distinguish between trusted and unknown software depending on one’s business operations. Identifying such “tells” and their implications can allow defenders to take even trusted items, such as code signing certificates, and narrow what is truly allowed or acceptable within their environments versus what is anomalous or suspicious.

Finally, the entire infection chain outlined above relies on a user interacting with a phishing message then executing an unknown binary from a cloud storage location. These items represent critical touch points for defensive response and monitoring—and user education. Through email security monitoring, organizations can identify, categorize, and filter providers for things such as landing pages and response emails to reduce attack surface. Furthermore, organizations can limit or completely block the download of files (or at least executable files) from external cloud storage locations to further reduce risk. Lastly, execution by the user of an unknown (even if signed) binary can be limited through either training or operating system controls to eliminate the ultimate stage of this attack sequence.

Overall, visibility into network communications, the ability to refine those communications with the support of external CTI sources, and combining this with host-based or malware-centric observations will enable defenders to identify, track, and hopefully mitigate potential ransomware events such as that described above. This whole-of-killchain approach, similarly documented with respect to BazarLoader by Red Canary in 2019, ensures detection at various stages of adversary operations. Through concerted effort and continued refinement, defenders will be able to identify “normal” activity within their environment and set that against abnormal traffic that may be related to malicious operations. As a result, defended organizations can gain some lead time over intruders, setting up proactive or preemptive defenses to limit exposure to campaigns as they materialize.

In this analysis, we identified an initial campaign and used related items to reveal a slightly earlier ransomware campaign likely related to the same adversary. By applying this process in a continuous, iterative fashion, we as network defenders and CTI professionals can continually reduce the scope and degree of movement for adversaries and improve the prospects of network defense. Marrying network security monitoring with network indicator enrichment through sources such as DomainTools can reveal campaigns in progress, while subsequent relations to file-based observations can cement these views to enable holistic network defense. Ultimately, network defenders must leverage all sources available to them in order to adequately respond to and detect such threats, with the goal of minimizing adversary dwell time and maximizing defender opportunities for response and recovery.

This content was originally published here.

Laat een reactie achter

Het e-mailadres wordt niet gepubliceerd.