Like so many Internet risks these days, zombie PCs represent a complex threat.

Cybercriminals are becoming increasingly sophisticated and are utilizing a variety of nefarious tools and tricks to do their dirty work. As mentioned earlier, one common vector of infection is via an infected email attachment, which, if not detected and removed by your anti-virus protection, can lead to a zombie infection. Here's how it might happen - opening an infected email attachment can install the malicious software, which can then open a port on your PC (if not protected by a firewall) to allow a hacker to utilize it to send or infect your PC with spyware (if not protected by anti-spyware software).