Deep Instinct recently detected and prevented an unknown dropper infection in a customer environment.
Upon further analysis, the dropper was found to be attempting to download a file from GitHub. While the file it was attempting to download was offline, the account was found to be hosting an additional malware executable intended to steal Crypto-Currencies from the victim machine.
While this is not the first time GitHub has been used to host malware, this is still considered a relatively rare occurrence.
The dropper, a small ~30KB executable written (in somewhat amateurish fashion) in .NET, features some basic evasion, designed to avoid VirutalBox and SandBoxie environments:
It will disable the Windows Security Service (sc stop wscsvc) and Internet Connection Sharing (sc stop SharedAccess), as well as some additional Operating System functionalities like the ability to open the Windows Task Manager or use Windows command-prompt.
As mentioned above, the hardcoded payload URL the dropper tried to contact was offline (likely due a typo), but the GitHub account was active and was found to be hosting an additional malicious executable:
Once analyzed, the malware was found to be an information stealer targeting Crypto-Currency related folders.
It will iterate through the %APPDATA% folder and look for subfolders belonging to Crypto-Currency related applications. If a folder is found, it will steal contained wallet.dat files from the folder, and upload them to a remote free-hosted server:
The malware targets ~300 crypto-currency related folders, including:
To name just a few.
A curious (and funny) artifact found during analysis, was a fairly unique debug path used in the crypto-stealer’s development:
Cross-referencing various sources and telemetry for similar samples, we managed to uncover several additional variants of this Crypto-Currency stealer being delivered by the same type of dropper from less-than-reputable hosting as well as an Email message, equally as amateurish in style as the dropper, used in the malware’s distribution:
The original bitcoin stealer was removed (likely, the result of us reporting it), but the repo and account are still live. Now, the repo hosts a PC-Cyborg Ransomware.
With the holiday season fast approaching, attackers of every variety are ramping up their efforts to steal what they can. This often includes a hosting service that is intended to appear legitimate, such as GitHub, but offers attackers a robust hosting platform, with nearly unlimited bandwidth. Plus, it’s very good reputation entails it is less likely to be blocked by various network security measures.
We have reached out to GitHub to report the offending account.
Droppers (sha256), analyzed sample in bold
Crypto-Stealer payloads (sha256), analyzed sample in bold
Crypto-stealer infection URLs
hxxps://github.com/misterbtc2020/btc/blob/master/bitcoin.exe?raw=true (broken URL)
hxxps://github.com/misterbtc2020/btcgenerator/blob/master/bitcoingenerator.exe?raw=true (fixed URL ;))
Crypto-Stealer “Wallet Drops”