SANS ISC: Kwampirs Targeted Attacks Involving Healthcare Sector

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There is no honor among thieves. Even after some ransomware gangs claimed to seize targeting the healthcare sector, attacks continue to happen. But ransomware isn't alone. Last week, the FBI updated an advisory regarding the Kwampirs malware, pointing out the healthcare sector as one of its targets. Kwampirs isn't picky in its targeting. It has been observed going after various sectors (financial, energy, software supply chain, and healthcare, among others). One differentiator of Kwampirs is its modular structure. After penetrating a particular target network, the malware will load appropriate modules based on the targets it encounters. In general terms, Kwampirs is a "Remote Admin Tool" (RAT). It provides access to the target and can be used to execute additional payloads at the attacker's choosing.

The modular nature makes it difficult to enumerate the capabilities of the tool. Likely, addons are developed continuously as new capabilities are required to penetrate a particular network.

Kwampirs exhibits several behaviors that put it in the "Advanced Persistent Threat (APT)" category:

• It is patient. Kwampirs does not launch fast "hit and run" attacks. Instead, it can infiltrate a network and only communicate daily, asking for updates. I took some networks three years to detect Kwampirs.
• Kwampirs infiltrates software vendors and uses them to spread to customers. These supply chain attacks are well suited to target specific industries.
• It does not have a clear financial motive, like stealing PII or payment card data. The malware has not been observed destroying or encrypting data for ransom.

Kwampirs will likely enter your network undetected as part of a software update from a trusted vendor. Anti-malware solutions will detect past versions. But do not put too much trust in anti-malware to detect the next version that is likely tailored to your organization.

There are a few indicators that have been observed in the past, and it is certainly important to verify your network that you are not already infected. See the prior FBI bulletins for more details and Yara signatures.

But of course, this behavior is going to change. For future versions of this (and other threats), it is useful to abstract these signatures:

Check for new services popping up in your network. Do not look just for specific names like "WmiApSrvEx", but investigate any service that you haven't see before
New processes. This is tricky and maybe too noisy.
New files being added to system folders. Again, don't focus on the specific names.
Kwampirs will also propagate through administrative shares. Deception techniques are an excellent option to catch this type of behavior.

Of course, I always like network detection techniques to identify malicious behavior. For Kwampirs, this may be a bit tricky, but it depends on what exact version you encounter. Some versions apparently will connect to an IP address directly, skipping DNS. Outbound connections without a DNS lookup returning the target IP should be one of your standard signatures. In the past, Kwampirs used some odd domain names that may stick out. For example, it used the "tk" top-level domain, which has sadly become almost an indicator of compromise in itself. Declaring yourself authoritative for .tk and redirecting queries to a sensor is an excellent way of detecting these and many other exploits. I probably wouldn't spend too much time looking for the specific hostnames listed in the FBI advisory. These hostnames tend to be very ephemeral, and they are not going to "last" very long. But a historical search of your DNS logs (did I mention Zeek?) may be appropriate.

If you find anything interesting, please let us know. Refer to the FBI advisories I uploaded here for more detailed IOCs. 

[1] https://isc.sans.edu/diaryimages/Kwampirs_PIN_20200330-001.pdf
[2]  https://isc.sans.edu/diaryimages/FLASH-CP-000111-MW_downgraded_version.pdf
[3] https://isc.sans.edu/diaryimages/FLASH-CP-000118-MW_downgraded_version.pdf

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Johannes B. Ullrich, Ph.D. , Dean of Research, SANS Technology Institute
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