Security researchers observed sextortion scammers launching new attack campaigns that leverage image spam and other clever techniques to trick users into fulfilling their demands.

According to Cisco Talos, attackers are currently using several different tactics to make their emails evade detection by anti-spam filters. Some of these methods aren’t entirely new. For instance, some attackers are using image spam, a technique that goes back to at least 2005, by sending along only an image of a sextortion-based ransom note.

The problem with this approach, however, is that victims can’t follow the note’s instructions or copy the attacker-owned bitcoin address included in the image. This snag lowers the chances of the attackers receiving payment.

Some of the tactics are more recent. For instance, some threat actors are seeking to trick anti-spam filters by using a combination of usernames in comments, plaintext letters and HTML characters. Others are sending along ZIP files that purport to contain evidence of the attackers having compromised the target’s computer.

Cisco Talos researchers weren’t able to examine the contents of these password-protected archives, but they believe that any files included likely consist of junk data.

New Attack Waves, New Techniques

Sextortion scammers have been busy since at least July 2018, when researchers discovered the first attack waves. As reported by Krebs on Security, those emails leveraged passwords already compromised in publicly disclosed data breaches to trick users into fulfilling the attacker’s demands. One month later, Naked Security spotted another wave using redacted phone numbers toward the same end.

Since then, cybercriminals have grown increasingly more creative. For instance, Proofpoint observed one wave that attempted to infect users’ computers with GandCrab ransomware. Another variant relied on a fake CIA investigation to scare users into paying, as reported by Tripwire.

How to Defend Against Sextortion Scams

Security professionals can help defend their organizations against sextortion scams by using ahead-of-threat detection to spot potentially malicious domains before threat actors have the chance to use them against employees.

As always, organizations should also create an ongoing security awareness training program that teaches users to be on the lookout for social media scams and other ruses such as sextortion-based ploys.

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