How many universal packers exist in the world today? According to our conservative estimate, there are over 100 types, but some specialists believe this number to be close to 200. Using this arsenal of specialized software, virus writers create new modifications of the same viruses with hardly any effort.

As soon as a new virus appears, it can be processed using a packer or encryption tool (this takes mere seconds), verified to ensure that it is operational and sent out into the world. As a result, there will be two modifications of the same virus on the Internet.
Some antivirus vendors try to solve the problem the easy way. They add signatures for viruses and their modifications (including packed versions) to their antivirus databases, but do not include support for packing utilities. As a result, when a newly-packed virus appears, these vendors need to add a new signature to their antivirus databases. However, if an antivirus product supports the packer, the new virus modification is detected automatically, without having to add a new signature to the database.

Naturally, not all antivirus vendors use this approach. But, packers and encryption tools are regularly updated and antivirus vendors need to keep track of these new versions in the same way that they track the appearance of new viruses.

After many consultations with antivirus vendors and independent experts, we selected 21 types of packer out of the variety that exists today.

The choice of packers was based on the following criteria:

1. The popularity of a particular packer among virus writers.
2. Our own analysis of packers and their use as a tool to conceal malicious code.

We used the latest versions of packers publicly available on the Internet at the time of testing.