Bck/ZxShell.A is a backdoor that allows hackers to gain remote access to the affected computer in order to carry out actions that compromise user confidentiality and impede the tasks performed on the computer.
It captures certain information entered or saved by the user, with the corresponding threat to privacy:
passwords saved by certain Windows services.
It sends the gathered information to a remote user by any available means: email, FTP, etc.
- In the local network:
it generates a large amount of network activity and consumes bandwidth.
It reduces the security level of the computer:
it terminates processes belonging to security tools, such as antivirus programs and firewalls, leaving the computer defenseless against attacks from other malware; it notifies the attacker that the computer has been compromised and is ready to be used maliciously; it listens on open ports in order to control the computer remotely; it awaits remote-control orders received through
IRC, HTTP, FTP or other channels.
It uses stealth techniques to avoid being detected by the user:
- It uses techniques included in its code to hide itself while it is active.
- It terminates processes corresponding to several security tools, such as antivirus programs and firewalls, to prevent detection.
Bck/ZxShell.A does not spread automatically using its own means. It needs an attacking user's intervention in order to reach the affected computer. The means of transmission used include, among others, floppy disks, CD-ROMs, email messages with attached files, Internet downloads, FTP, IRC channels, peer-to-peer (P2P) file sharing networks, etc.