What is a botnet?
The term bot is short for robot. Criminals distribute malware (malicious software) that can turn your computer into a bot, also called a zombie. When this occurs, your computer can perform automated tasks over the Internet without your knowledge.
Criminals typically use bots to infect large numbers of computers. These computers form a network, or a botnet.
Botnets can be used to send out spam email messages, spread viruses, attack computers and servers, and commit other kinds of crime and fraud. If your computer becomes part of a botnet, it might slow down and you might be inadvertently helping criminals.
How to tell if your computer is infected with malware
It’s not always easy to tell if your computer has been infected with malware. If it is unusually slow, crashes or stops responding frequently, for example, these problems might be signs that your computer has been infected. However, the same problems might also point to hardware or software issues that have nothing to do with malware. Because it’s difficult to tell the reasons for your computer’s unusual behavior, we suggest that you follow these steps:
- Get a more complete list of symptoms.
- If, based on the complete list of symptoms, you think your computer has been infected, let Microsoft help you diagnose the problem and solve it.
How to help avoid malware
Cybercriminals use two basic strategies to penetrate your computer’s defenses and enlist computers in their botnets:
- They install malware on a computer by taking advantage of unintended vulnerabilities in its software or by breaking into accounts guarded by weak passwords.
- They try to trick you into installing their malware.
To help secure your computer against bots, follow the advice below. For specific how-to info, see How to boost your malware defense and protect your PC.
Strengthen your computer’s defenses
- Install antivirus and antispyware programs from a trusted source. Anti-malware programs scan and monitor your computer for known viruses and spyware. When they find something, they warn you and help you take action.
- Keep all software up to date. Regularly install updates for all your software and subscribe to automatic updates wherever possible.
- Use strong passwords and keep them secret. Use our password checker to determine the strength of your password.
- Never turn off your firewall. A firewall puts a protective barrier between your computer and the Internet. Turning it off for even a minute increases the risk that your PC will be infected with malware.
- Use flash drives cautiously. Putting your flash drive (sometimes called a thumb drive) in a computer that is infected could corrupt the drive, and ultimately your computer.
Do not be tricked into downloading malware
Attackers can enlist your computer in a botnet by:
- Delivering malware in downloads that you think are pictures or movies, or through links that you click in email or instant messages (IM), or on a social network.
- Scaring you into clicking a button or link they supply with fake warnings that your computer has a virus.