Users Warned of New Aerst, ScareCrow, and Vohuk Ransomware Families

Fortinet’s security researchers have shared information on three new ransomware families named Aerst, ScareCrow, and Vohuk.

Targeting Windows computers, these are typical ransomware families that encrypt victim files and demand a ransom payment in exchange for a decryption key. This new ransomware has been used in an increasing number of attacks.

Aerst was seen appending to encrypted files the ‘.aerst’ extension and displaying a popup window containing the attacker’s email address, instead of dropping a typical ransom note.

The popup window contains a field where the victim can enter a purchase key required to restore the encrypted data. Aerst deletes Volume Shadow copies to prevent file recovery.

Vohuk does drop a ransom note – readme.txt – asking the victim to contact the attackers via email. Seemingly under continuous development, the malware assigns a unique ID to each victim.

This ransomware family appends the ‘.vohuk’ extension to the encrypted files, replaces file icons with a red lock icon, and changes the desktop wallpaper with its own.

“The ransomware leaves a distinctive mutex, ‘GlobalVohukMutex’, which prevents different instances of Vohuk ransomware from running on the same system,” Fortinet explains.

The malware has been mainly targeting users in Germany and India.

ScareCrow’s ransom note, named ‘readme.txt’, instructs victims to contact the attacker using one of three Telegram channels. The threat appears to be the most widespread, with files submitted from the United States, Germany, India, Italy, the Philippines, and Russia.

Fortinet has identified some similarities between ScareCrow and Conti, such as the use of the CHACHA algorithm for encryption, and the use of the WMI command-line utility to delete Volume Shadow copies, which suggest that ScareCrow’s developers might have used Conti source code leaked earlier this year.

The ransomware’s developer has encrypted each command string in the malware, including DLL names, API names, and even command strings, with a different decryption routine. ScareCrow appends the ‘.crow’ extension to the encrypted files.

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