You’re working at your computer, when all of a sudden — BAM! — you get a pop-up notification that your PC is infected with a virus and you must “click here." to run a scan or install antivirus software.

This is a common scareware tactic used by hackers to get you to click and download a virus. Legitimate companies would never deliver that type of pop-up to you.

Often it will appear to be a system alert or a Microsoft operating system alert. Regardless of how legitimate it looks, NEVER click on the site or the pop-up. The safest thing to do is close your browser; do not click on the X, Close or Cancel button in the pop-up or on the site. Clicking on anything on the page or the pop-up will trigger a virus download.

If that won’t work, bring up your task manager — hold down Control + Alt + Delete on a PC or Command + Option + Esc to Force Quit on a Mac — and close the web browser or application where it appeared. Next, notify your IT staff that this has happened, so they can double-check with a legitimate scan to see if your computer was infected.

Alan Edwards, CISM, is chief information officer at Computerware, Inc., in Vienna, Virginia.