Use anti-virus software and keep it up-to-dateIf you haven't installed anti-virus software on your computer, do it now. Anti-virus software can detect many — but not all — forms of malicious software before they have a chance to affect your computer. When you purchase anti-virus software, look for one that includes anti-spyware. Most anti-virus software can automatically download updates for you. Check to make sure your software is downloading updates correctly.
Keep all your software up-to-dateYou can prevent many problems by regularly checking for and installing updates for your programs, including your operating system, browser, messaging software, and other software. Many programs include a feature that automatically checks for updates. Be wary of clicking links in emails claiming to have updates for your software; it is safer to type the address of the web site into your browser’s Address bar to visit the site directly.
Check your security settingsMost operating systems (such as Windows XP) have a built-in firewall and other safeguards to prevent unauthorized access to your computer. Check your operating system to make sure it's set up so that your computer is protected. Install any security updates or patches for your operating system promptly.
Be careful opening email attachmentsConsider turning off the feature in your email programs that automatically opens attachments. If you receive an attachment you aren't expecting, do not open it. Before you open any email attachment — even if it's from someone you trust — scan it using anti-virus software. Yahoo! Mail automatically scans all email attachments for viruses.
Don't install unfamiliar programsThink carefully before installing or running new software, such as freeware or shareware programs available online. Only download software from a source you trust. Do not install software if you cannot verify that it's from a trusted source. Make sure you know what the software will do and how it will affect your computer. Malicious software (like viruses and spyware) often masquerade as legitimate and even useful programs. For example, you might be tempted to download a program that claims to keep your computer clock synchronized with an official clock. But if that program contains adware or spyware, it could also display advertising pop-ups whenever you're online or keep track of where you go on the Internet.
Be wary of pop-up and email warningsDon't believe every warning you read — especially pop-up warnings that you see while you're surfing the Web. Unscrupulous companies use pop-up ads to display false warnings about your computer. Ignore them.
Do NOT click any button in the pop-up (such as a "Close" or "No" button) or the Close box that may appear in the upper-right corner of the pop-up. Closing a pop-up in that way might actually install a virus or other malicious software on your computer. To close a pop-up ad, press Ctrl-W (if you're using a Windows computer) or Command-W (on a Mac computer). You may receive an email warning that claims to be from a computer "expert" warning you of a virus. These are usually hoaxes. Do not follow the steps described in any email unless you're sure the threat is real.