Povlsomware (Ransom.MSIL.POVLSOM.THBAOBA) is a proof-of-concept (POC) ransomware first released in November 2020 which, according to their Github page, is used to “securely” test the ransomware protection capabilities of security vendor products. Povlsomware has not garnered much attention at the moment, being talked about in only a few sites — however, it has some interesting characteristics, notably its compatibility with the post-exploitation tool Cobalt Strike (which has been linked to other ransomware families such as Ryuk and DoppelPaymer) — giving the malware capabilities beyond what its seemingly simple infection routine shows. Furthermore, because the malware is open-source, anyone can modify and use it as part of their attack chain.

Figure 1. The ReadMe page from the Povlsomware GitHub page

Figure 2. Ransom note from a sample found in the wild written in Russian

At first glance, Povlsomware seems to follow a fairly typical ransomware routine. First, it will check to see if it is running in privileged mode, after which it will attempt to delete backups via Windows Management Instrumentation (WMI).

Based on the latest source code, the files it tries to encrypt are fairly standard, which includes commonly used file types such as word documents, PDF files, audio and video files, and RAR archives.

It will also avoid directories containing the following strings:

All Users\\Microsoft\\
AppData\\
C:\\Program Files
\\Povlsomware\\
\\Povlsomware-master\\
C:\\ProgramData\\
$Recycle.Bin
\\source\\
Temporary Internet Files
C:\\Windows

After it is done with encryption, Povlsomware will display the list of affected files along with the ransom note.

Figure 4. The ransom note displayed by Povlsomware after it has encrypted its victim’s files

One interesting characteristic about Povlsomware is that it is an extensionless ransomware — that is, it does not append additional extension names to the files it encrypts. This means that encrypted files will still look the same when viewed through a directory but will not work properly when the user tries to open them.

Beyond its routine, the more concerning aspect of Povlsomware is how the authors claim it is coded —its Cobalt Strike compatibility allows it to perform in-memory loading and execution. This “execute-assembly” feature of Cobalt Strike allows the execution of a payload binary through memory only and does not drop any payload binaries into the victim’s system. This makes the payload more difficult to detect (since it does not rely on the tools found in the target system) and analyse due to the lack of payload binaries being dropped.

Figure 5. Screenshot from the Povlsomware GitHub page showing the Cobalt Strike integration

Figure 6. Screenshot from the Povlsomware GitHub page showing the malware being run under Cobalt Strike

What makes Povlsomware notable is not what it has already accomplished — there have been few, if any, notable incidents involving the malware at the time of writing — but how it can potentially be used. Although ostensibly advertised as an “educational” tool, its access to Cobalt Strike capabilities and its open-source nature make it a potentially dangerous malware in the hands of an experienced ransomware operator.

Security recommendations and solutions

Ransomware attacks can come in many forms. At the simplest end of the spectrum, you have infection vectors such as phishing emails that will deploy the malware if the user accesses them. More complicated campaigns, on the other hand, might make use of complex infrastructure involving the use of tools such as Cobalt Strike or Mimikatz as part of the infection routine.

Given the wide array of tools and techniques that ransomware operators use, organisations and individual users have to be vigilant on all fronts to protect their machines and systems from ransomware attacks. The following security best practices can help with this:
Limiting access to shared network drives and turning off file sharing lessens the probability that a ransomware infection spreads to other devices.
Employing authentication options that include multi-factor authentication strengthens the security of user accounts, minimising opportunities for account theft or compromise.
Enforcing the principle of least privilege — where users only have access to the sections of the system that they need— can help prevent attackers from running tools and software used by ransomware.
Using application controls can help prevent attacks that leverage remote access software.
Regular patching and updating of software and systems reduce the chance for an attacker to exploit a vulnerability that is part of the infection routine.
Regularly backing up files, preferably using the 3-2-1 rule, still remains an effective method of protecting data in the event of a successful ransomware infection.

Organisations can also take advantage of security technologies such as Trend Micro XDR ^TM, which collects and correlates data across endpoints, emails, cloud workloads, and networks to provide better context to attacks in a single console. This allows security and IT teams to respond to ransomware and other threats faster and more effectively.

Indicators of Compromise (IOCs)

SHA-256	Detection	TrendX
e05c74663775baf3ee37430d4662f7a9c89d63a752af5448c273e6b70fd9aec74	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
9effa31cbcf5e90fc0955b363871a4ef54ffd7634a0095673004b39e9036ef94	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
2aca9d08bacd2df13dd0475cc624fddec3fcc13495cbc7fc4f715764cb3c7ebe	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
c740cbdd79c5ef5fae2b9388cd57dcd76ab491cdb94bcacd525b599b12d25f88c	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
e08456212a2d597ba26456df8cbf48890a4350d9a8aba436c65acfec171ad468	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
6a61bdcdaf9b8b9dd0a5328680acee9db9d0b64166cbf1cf73046a8e0c4efec8	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
f27b13e25bc39c222847c150488b5c404042fd526023d6ac8866e306e4975349	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
6c7485988ca145b02f564b8aae89133acf1aec6fae0db44be26cd3c8e87a6d1c6a	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
d8cb6bc96ed3c980013addb9af4f61fdfefc5e3373c36e821062c2dae565dd75	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
37ca7a3b52d6cb9d9ebb9319c5f28f7b1e0ebb338bf732ace170684eb193b10e	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
cb2ef26d028621b5b438e5386daf1f06fc986d88d31c99b9833b4b906e6f0f33	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
de17f48967192dbd33ac67d752c7c4de441204d1da58b9801a90775e0265a66a	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
260950708c993ed1585a98952493bbaca92a8162439887b510ca832713898b75	Ransom.MSIL.POVLSOM.THBAOBA	N/A
3e6783288c3387437b25eb9f990cc9329acffb073baf7bb954e087c3733cfb2e	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
124e33009fc91c9964f5c44e4dc42ef7ae787bbb375305b95cbd7ee8014f080c	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
9a355fc10fae9e7906c34d8850a2efc5c93a3a1274coe3b122f5d6944b2d33f837	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF041
2a6a5f6842b7f40c905aec44c43b4a9a999dadbcbc06f7d320ea4e96cc96e899f	Ransom.MSIL.POVLSOM.THBAOBA	N/A
78c2f745aa5ae027dad5fae67aec892cf6b05fd418f72031fb5d744b63bdf11200	Ransom.MSIL.POVLSOM.THBAOBA	Troj.Win32.TRX.XXPE50FFF04 1

Povlsomware Ransomware Features Cobalt Strike Compatibility

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Indicators of Compromise (IOCs)

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