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Evolution of Locky – A Cat & Mouse Game

In the on-going game of cat and mouse between cyber attackers and defensive internet security providers, the appearance of a new tactic from the Locky family of Ransomware comes as no surprise.

As we discussed in February this year, Locky targets victims through seemingly legitimate email attachments. Once the victim clicks on the attachment the malicious macro begins encrypting the users’ files.

Given the nature of this environment, security experts are constantly working on ways to stop Locky, coming up with solutions that will render it ineffective.

Distribution of the latest attack

In the latest development, cyber attackers have come up with new tactics to bypass security. The malware is still distributed via email attachments, but no longer uses a Trojan. These emails have varying names and subject lines to attract the victims’ attention and usually contain Zip files.

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The Malware skips the downloader Trojan and gets the Locky variant in DLL format, and is then executed using Windows rundll32.exe. By using a script file as well as a DLL, instead of a Trojan and .exe, Locky is not immediately detected and blocked, and the Ransomware can begin its course.

To further ensure its success cyber attackers have given Locky an added fall-back mechanism, this means that the malware will still be able to complete its actions even in cases where it can’t reach command and control servers. The weak point in this is that the encryption key is the same for every computer.

These attacks appear to present in weekly waves and have already targeted victims in North and South America, and Europe, as well as attacks in Africa and Asia.

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In order to protect yourself, security experts suggest setting up filters for script files that arrive via email, as well as ensuring your antivirus is up to date. Advanced solutions such as Panda’s Adaptive Defence allow for active classification of every running application by leveraging Endpoint Detection & Response (EDR) technologies. This means that you have a greater chance of defending your network against today’s advanced threats.

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