Proofpoint uncovers new MarsJoke ransomware, then Kaspersky finds the fix

Government and educational institutions are the targets of a new ransomware strain called MarsJoke, a complex variant with 'hundreds of thousands of messages' including URLs leading directly to malware.

"The explosion of ransomware we're facing makes MarsJoke feel like 'just another ransomware' - but to the state agency or high school that ends up paying sizeable ransoms or losing critical data, this is hardly ordinary," says Kevin Epstein, VP of threat operations.

Proofpoint discovered MarsJoke in August, however large-scale email attacks weren't detected until September.

The company says the ransomware targets organisations similar to what CryptFile2 targeted in August, which leads them to believe that Kelihos, a common botnet distributor, is behind these attacks.

Further research from Kaspersky Lab also enabled them to decrypt files compromised in ransomware attacks, using a loophole in the key generator. The company is offering the RannohDecryptor freely to all those infected by the MarsJoke ransomware.

MarsJoke's September attack included email URL links that led to an executable file, 'file_6.exe'. Proofpoint says the emails looked genuine and used a range of subject lines with stolen branding to fool users.

"Three things set this campaign apart from other recent ransomware attacks: the use of so-called hosted ransomware, the targeting, and the scale. While it hasn't reached the scale of an average Locky attack, combined with the known targeting, this MarsJoke campaign is significant," Epstein says.

Once the ransomware successfully infects a system, a dialogue appears and demands 0.7 bitcoins within 96 hours, or their files are deleted.

Proofpoint believes the campaign's targeting and message volume also suggest that attackers are attempting to monetise new variants as well as old strains to 'saturate potential victims'.