Joe Desimone and Samir Bousseaden reported that ,”Executables with valid code signing certificates are frequently monitored to a lesser extent than unsigned executables. Their use allows attackers to remain undetected for a longer period of time.”
Researchers have provided details of an evasive malware campaign that uses valid code signing certificates to bypass security defences and remain undetected, with the goal of deploying Cobalt Strike and BitRAT payloads on compromised systems.
Elastic Security uncovered a stealthy malware campaign that leverages valid code signing certificates to evade detection. A novel malware loader, BLISTER was used to execute second stage malware payloads in-memory and maintain persistence, The identified malware samples have very low or no detections on Virus, TotalElastic provided layered prevention coverage from this threat out of the box.
The use of a valid Sectigo code signing certificate is an important aspect of this campaign. Adversaries can either steal legitimate code-signing certificates or purchase them directly or through front companies from a certificate authority. Executables with valid code signing certificates are frequently subjected to less scrutiny than unsigned executables. Their use allows attackers to remain undetected for a longer period of time.
We reported the activity to Sectigo in a responsible manner so that they could take action and revoke the abused certificates. The details of the compromised certificate are shown below. Malware signed with this certificate has been seen as early as September 15, 2021.
Issuer: Sectigo Public Code Signing CA R36
Issued to: Blist LLC
Serial number: 2f4a25d52b16eb4c9dfe71ebbd8121bb
Valid from: Monday, August 23, 2021 4:00:00 PM
Valid to: Wednesday, August 24, 2022 3:59:59 PM
Blister poses as a legitimate library called “colorui.dll” and is distributed through a dropper called “dxpo8umrzrrr1w6gm.exe.” Following execution, the loader is designed to sleep for 10 minutes, most likely to avoid sandbox analysis, before establishing persistence and decrypting an embedded malware payload such as Cobalt Strike or BitRAT.
Finally the researchers concluded that , “Once decrypted, the embedded payload is loaded into the current process or injected into a newly spawned WerFault.exe [Windows Error Reporting] process”.
Indicator Of Compromise
| Indicator | Type | Note |
|---|---|---|
| F3503970C2B5D57687EC9E31BB232A76B624C838 | SHA1 | Code-signing certificate thumbprint |
| moduleloader.s3.eu-west-2.amazonaws.com discountshadesdirect.com bimelectrical.com clippershipintl.com | Domain name | Malware c2c |
| 188.68.221.203 93.115.18.248 52.95.148.162 84.38.183.174 80.249.145.212 185.170.213.186 | IP Address | Malware c2 |
| ed6910fd51d6373065a2f1d3580ad645f443bf0badc398aa77185324b0284db8 cb949ebe87c55c0ba6cf0525161e2e6670c1ae186ab83ce46047446e9753a926 7b9091c41525f1721b12dcef601117737ea990cee17a8eecf81dcfb25ccb5a8f 84a67f191a93ee827c4829498d2cb1d27bdd9e47e136dc6652a5414dab440b74 cc31c124fc39025f5c3a410ed4108a56bb7c6e90b5819167a06800d02ef1f028 9472d4cb393256a62a466f6601014e5cb04a71f115499c320dc615245c7594d4 4fe551bcea5e07879ec84a7f1cea1036cfd0a3b03151403542cab6bd8541f8e5 1a10a07413115c254cb7a5c4f63ff525e64adfe8bb60acef946bb7656b7a2b3d 9bccc1862e3e5a6c89524f2d76144d121d0ee95b1b8ba5d0ffcaa23025318a60 8a414a40419e32282d33af3273ff73a596a7ac8738e9cdca6e7db0e41c1a7658 923b2f90749da76b997e1c7870ae3402aba875fdbdd64f79cbeba2f928884129 ed241c92f9bc969a160da2c4c0b006581fa54f9615646dd46467d24fe5526c7a 294c710f4074b37ade714c83b6b7bf722a46aef61c02ba6543de5d59edc97b60 | sha256 | Signed Droppers |
| df8142e5cf897af65972041024ebe74c7915df0e18c6364c5fb9b2943426ed1a 2d049f7658a8dccd930f7010b32ed1bc9a5cc0f8109b511ca2a77a2104301369 696f6274af4b9e8db4727269d43c83c350694bd1ef4bd5ccdc0806b1f014568a a34821b50aadee0dd85c382c43f44dae1e5fef0febf2f7aed6abf3f3e21f7994 7cd03b30cfeea07b5ea4c8976e6456cb65e09f6b8e7dcc68884379925681b1c4 81edf3a3b295b0189e54f79387e7df61250cc8eab4f1e8f42eb5042102df8f1f 44e5770751679f178f90ef7bd57e8e4ccfb6051767d8e906708c52184bf27f32 0a7778cf6f9a1bd894e89f282f2e40f9d6c9cd4b72be97328e681fe32a1b1a00 a486e836026e184f7d3f30eaa4308e2f0c381c070af1f525118a484a987827c1 359ffa33784cb357ddabc42be1dcb9854ddb113fd8d6caf3bf0391380f9d640a 863228efa55b54a8d03a87bb602a2e418856e0028ae409357454a6303b128224 d0f934fd5d63a1524616bc13b51ce274539a8ead9b072e7f7fe1a14bb8b927a6 c0f3b27ae4f7db457a86a38244225cca35aa0960eb6a685ed350e99a36c32b61 216cb4f2caeaf59f297f72f7f271b084637e5087d59411ac77ddd3b87e7a90aa 00eb2f75822abeb2e222d007bdec464bfbc3934b8be12983cc898b37c6ace081 25a0d6a839c4dc708dcdd1ef9395570cc86d54d4725b7daf56964017f66be3c1 3c7480998ade344b74e956f7d3a3f1a989aaf43446163a62f0a8ed34b0c010d0 5651e8a8e6f9c63c4c1162efadfcb4cdd9ad634c5e00a5ab03259fcdeaa225ac ba3a50930e7a144637faf88a98f2990a27532bfd20a93dc160eb2db4fbc17b58 fa885e9ea1293552cb45a89e740426fa9c313225ff77ad1980dfea83b6c4a91c bee3210360c5d0939c5d38b7b9f0c232cf9fbf93b46a19e53930a1606bda28a5 56ca9ea3f7870561ed3c6387daf495404ed3827f212472501d2541d5ccf8b941 c61d2ba1e001c137533cd7fb6b38fe71fee489d61dbcfea45c37c5ec1bcf845c 17ea84d547e97a030d2b02ac2eaa9763ffb4f96f6c54659533a23e17268aabab ca09d9cd2f3cfcc06b33eff91d55602cb33a66ab3fd4f540b9212fce5ddae54a 6c6f808f9b19e1fab1c1b83dc99386f0ceee8593ddfd461ac047eae812df8733 | sha256 | Unsigned BLISTER Loader DLL |
| afb77617a4ca637614c429440c78da438e190dd1ca24dc78483aa731d80832c2 516cac58a6bfec5b9c214b6bba0b724961148199d32fb42c01b12ac31f6a6099 8ae2c205220c95f0f7e1f67030a9027822cc18e941b669e2a52a5dbb5af74bc9 fe7357d48906b68f094a81d19cc0ff93f56cc40454ac5f00e2e2d9c8ccdbc388 af555d61becfcf0c13d4bc8ea7ab97dcdc6591f8c6bb892290898d28ebce1c5d 96bf7bd5f405d3b4c9a71bcd1060395f28f2466fdb91cafc6e261a31d41eb37a f5104d0ead2f178711b1e23db3c16846de7d1a3ac04dbe09bacebb847775d76d 8e22cf159345852be585bc5a8e9af476b00bc91cdda98fd6a3244219a90ac9d9 d54dfedda0efa36ed445d501845b61ab73c2102786be710ac19f697fc8d4ca5c | sha256 | Signed BLISTER Loader DLL |
| Launcher V7.3.13.exe GuiFramwork.exe ffxivsetup.exe Predictor V8.21 – Copy.exe Predictor Release v5.9.rar PredictorGUI.exe Readhelper.exe dxpo8umrzrr1w6gm.exe Pers.exe razer.exe Amlidiag.exe Modern.exe iuyi.exe Cleandevicehelper.exe installer.exe | File name | Dropper Names |
| Holorui.dll Colorui.dll Pasade.dll Axsssig.dll Helper.CC.dll Heav.dll Pasadeis.dll Termmgr.dll TermService.dll rdpencom.dll libcef.dll tnt.dll | File name | BLISTER DLL Names |
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