The BKA Trojan still spreading through emails containing fake invoices

Even though the fraudsters behind the BKA Trojan (aka Ransom Trojan) have been caught by the police, there are still a lot of emails spreading the Trojan in circulation.

One of these emails drew my attention because it was addressed directly to me and because of the way in which it is constructed.

hse24-rechnung

The email pretends to come from the well-known online shopping portal hse24.de and it is addressed to only the recipient in the From field.

It contains in the body the first and last name taken probably from the email address, thus being very convincing for the unaware user. The same formula is used to name the attachment – a zip archive with the name “Rechnung <first name> <last name>.zip” / “Invoice <first name> <last name>.zip”.

What is really interesting, inside the ZIP archive there is another ZIP archive called “Bestellung 16.02.2013 – Rechnung” / “Order 16.02.2003 – Invoice” containing a .com file. However, a brief analysis shows that this is just a normal executable created with Visual Studio containing the trojan ‘TR/Ransom.Foreign.acdb.1′. This method of packing the malware is very clever, because very few security solutions on gateways and most certainly no local solution, scans on more than one layer recursively inside archives. Using this technique the cybercriminals ensured that the payload goes through the security checks on its route to the user’s inbox.

Avira users don’t have to worry about this, all products detect this file as ‘TR/Ransom.Foreign.acdb.1′.

 

Sorin Mustaca

IT Security Expert