Sality.AY is a virus that spreads to other computers by copying its code to other files or programs.
It affects productivity, preventing tasks from being carried out:
- In the affected computer:
causes system slowdowns.
It reduces the security level of the computer:
it awaits remote-control orders received through
IRC; it changes system permissions, decreasing the security level.
It uses stealth techniques to avoid being detected by the user:
- It injects itself in running processes.
Sality.AY uses the following propagation or distribution methods:
- Exploiting vulnerabilities with the intervention of the user: exploiting vulnerabilities in file formats or applications. To exploit them successfully it needs the intervention of the user: opening files, viewing malicious web pages, reading emails, etc.
- Computer networks (mapped drives): it creates copies of itself in mapped drives.
- Computer networks (shared resources): it creates copies of itself in shared network resources to which it has access.
- File infection: it infects different types of files, which are then distributed through any of the usual means: floppy disks, email messages with attachments, Internet download, files transferred via FTP, IRC channels, P2P file sharing networks, etc.
Sality.AY uses the following infection strategies:
- Resident: once it has been run, the virus goes memory resident and stops functions belonging to the operating system. Therefore, every time the operating system or an application tries to access any of these functions, the virus will activate and infect new files.
- Stealth: when the virus is memory resident, it hides the modifications made to the boot sectors or files it has infected. These modifications are: changes in size, date, attributes, etc.
- Polymorphic: it encrypts itself in a different way with each infection it carries out. In order to do this, it uses different keys and operations. As a result, the virus has different characteristics in each new infection, which makes it difficult for antivirus pro-grams to detect this virus.
- Encrypted: it encrypts its code in order to make it difficult to detect. In order to carry out its infection, the virus decrypts itself and, once infection has been carried out, it encrypts itself again.
- EPO (Entry Point Obscuring): it infects programs that it allows to work as usual until a given point. Then, the virus takes control of the program and runs its own code.
- Cavity: it infects files without modifying their size or corrupting the data they contain, as it takes advantage of the cavities in these files to insert its code.