MirrorBlast phishing campaign targets financial companies

The attack has been linked to a long-standing Russian cyber crime group

A Russian cyber crime group has been targeting the financial sector with malware delivered by a familiar infection mechanism: Microsoft Office macros. 

Security company Morphisec identified the attack, dubbed MirrorBlast, which uses Microsoft Office macros to infect machines, a technique cyber criminals have used consistently over the years. 

The researchers analyzing the attack said it has been underway since September. It targets institutions in regions such as Canada, US, Hong Kong, and Europe. The researchers also saw similar activity in April. 

Morphisec tied the attack to TA505, a Russian cyber crime group that has been operating since 2014. The group often changes the malware it uses, according to the company.

The cyber crime gang uses phishing emails to mount the first phase of its attack. The initial email contains an Excel document that uses a macro. The macro, which can only run on 32-bit systems due to ActiveX compatibility issues, contains lightweight code designed to avoid detection. 

When run, the macro verifies an administrative account is running and then uses a Javascript command to start an installer program. This drops one of two malicious scripts. 

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These send the machine's information to a command and control (C2) server, including the computer name, user name, and a list of running processes. The C2 server then responds with a code telling the software how to proceed. 

The attack also uses a Google feedproxy URL with a fraudulent message urging the user to access a SharePoint or Onedrive file. This helps the attackers evade detection, Morphisec said. 

Certain aspects of the attack have led researchers to attribute it to TA505. This includes the infection chain and installer script. It also uses similar domain names to other TA505 attacks and an MD5 hash that matches one used in another of the group's attacks.

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