The Evilnum hacking group have been targeting European organisations that are involved in international migration, showing renewed signs of malicious activity within the group.
Evilnum is an advanced persistent threat (APT) that has been active since at least 2019 and had its campaign and tools exposed in 2020.
In 2020, ESET published a technical report describing the threat group’s tactics against compaines in the financial technology sector, using “homemade”, custom malware.
Zscaler’s analysts have discovered the latest exposure, having been tracking Evilnum’s activity since the beginning of 2022. They have captured various artefacts from the attacks.
The targeting and timing coincided with the Russian invasion of Ukraine, with key migration organisations receiving malicious emails containing macro-laden documents
The documents used by Evilnum in the campaign carry varying filenames, usually containing the term “compliance.” Zscaler identified at least nine different documents used, as mentioned in the IoC section of the report.
This decrypts and drops a malware loader (“SerenadeDACplApp.exe”) and an encrypted binary (“devZUQVD.tmp”), and also creates a scheduled task (“UpdateModel Task”) for persistence.
The loader performs preliminary checks and loads the binary under an extracted file name. The “Heaven’s gate” technique is used during the binary injection to evade AV detection.
This technique involves invoking 64-bit code in 32-bit processes. It has been mitigated in Windows 10, but Evilnum still likely uses it to target running older OS versions.
The backdoor that is loaded onto the compromised systems executes to decrypt the backdoor configuration, resolve API addresses from the libraries retrieved from configuration, and perform a mutex check, amongst other things.
Once it has embedded the encoded string inside the cookie header field by selecting one of the cookie type strings from the configuration, the backdoor picks a C2 domain and a path string from the configuration and sends a beacon network request. The C2 may answer with a new encrypted payload.
Also, the backdoor captures machine snapshots and sends them to he C2 via POST requests, exfiltrating stolen data in an encrypted form.
The report suggests that Evilnum is still an active threat.
The actor’s origin remains unknown, but in its most recent victimology indicates a state-level interest in espionage campaigns, liked by researchers to the Belarusian threat group “Ghostwriter.”