I can take control of your computer, but ONLY IF YOU LET ME. I need you to install me, so i'm disguised as a game or movie. I mostly attack Microsoft Windows computers, especially those that are out of date and don't have antivirus protection.
"Your computer is infected with 96 viruses. Click here to buy XP Antivirus 2009 to remove the threats."
Messages like are from rogue antivirus programs. They pop up when you visit hijacked websites. The "warning" tells you that your computer is infected with multiple viruses or spyware programs, and that you need to buy a specific program to get rid of them. In reality, you are infected by ONE malicious program, and that's the thing that's flashing the message. For more details of rogue antivirus programs, click here.
"Dear Friend, I'm sending you this great new music track/video clip/game. Do play it, I know you'll love it."
This is a trojan sent as an email attachment. Of course, it MIGHT be a genuine game or music track from a friend.. but be careful. If you're not absolutely sure it's genuine, don't open it. For more details of dangerous email attachments, click here.
"A friend has sent you a greetings card. Click here to see your wonderful card."
This email contains a link to click on, or an attachment called "greetings card", or something similar. It MIGHT be genuine, because there are perfectly respectable websites where you can send electronic greetings cards to friends, but it's best to assume that the thing is a trojan. DON'T click on it until you've found out who sent it and checked that it's genuine. For more details of dangerous email attachments, click here.
"Click here to download free music/videos/games/screensavers."
Many websites offer all sorts of attractive things for free: movies, videos, music, pictures, games, screensavers. Some of them will be genuine sites using the free gifts as advertising. But others will be criminal sites, whose "free gifts" are dangerous programs in disguise. For more details of good websites and bad, click here.