Recognizing a zombie computer can be incredibly difficult, because many of the signs can point to other problems, and most people do not know they are using a zombie until it is too late. A zombie computer often is compromised by virus files, so the computer often will slow down, and the computer may act weirdly. By checking firewall traffic, you can see if your computer is visiting places that you have not. Some virus scanners can find a zombie, but most hackers hide the zombie virus in a way that cannot be detected. Blacklist tools, if you do not partake in spamming activities, also can be used.
To make a zombie computer, a hacker infiltrates a computer and adds a virus file that puts the computer under his control. This file and the activity from the hacker often cause the computer to slow down, because the hacker is using many computer resources. The computer also may act oddly, with programs opening for no reason and users constantly being redirected to other websites. While these are signs of a zombie problem, they also can be signs of a less serious virus or the result of old hardware and software.
One of the best ways to see if you have a zombie computer is by checking your firewall — or other programs that report your activity — for outgoing traffic. This will list what websites and places you visit when using the Internet, and you should see websites that you frequent. If there is a large amount of outgoing traffic directed at sites you do not recognize, then you may be running a zombie. Small amounts of unusual outgoing traffic may not be indicative of a zombie but a result of common pop-ups and redirects that appear online.
Virus scanners can sometimes pick up on a zombie computer, but only if the hacker was not diligent. These programs will scan for common signs of viruses and zombie activity and, if they do pick up a zombie, they may be able to fix it. If the hacker placed the zombie virus file in a rootkit, then it usually is untraceable.
When you are running a zombie computer, it likely will be used for spamming and for sending large packets of information to other entities to shut them down. This will result in your computer being placed on blacklists for spammers. By entering your Internet protocol (IP) address in a blacklist tool, you may find you are blacklisted, which can indicate that you have a zombie computer. If you willingly engage in spamming activity, then this may not be effective.