When Reomel Lamores (aka ‘Spyder') unleashed the Love Bug virus on to an unsuspecting world nine years ago, it created havoc across the globe. In a single day I-LOVE-YOU infected 10 percent of all PCs connected to the web, causing about $5.5bn (£3.6bn) in damage.

What it didn't do was make Mr Lamores' life any better - or make him any richer. In those days, hackers worked only for fame, although many reformed script kiddies have since gone on to big things in legitimate coding.

Fast-forward to 2009 and the world of cybercrime is a very different one. Virtually all the estimated 1.66 million new threats released into the wild in 2008 were written and propagated with one thought in mind: money.

Malware is increasing exponentially, but nobody does it for fun, and hackers no longer work alone. More than 90 percent of attacks in 2008 were instigated by organised crime.

Getting into your PC is big business, then. In fact, it's almost as big as the industry that strives to protect it. So when a ‘big name' virus starts to make headlines and starts insinuating itself on to significant numbers of PCs, it's time to sit up and take note. That's exactly the case with the latest example, Conficker (aka Downadup).

Conficker was released in October and spread like wildfire, exploiting a network service vulnerability in all versions of Windows. Such was its virulence, it was able to infect more than nine million PCs by January 2009.

Its purpose was to send spam and generate revenue via antivirus scareware. It was designed to create a problem and then offer to ‘solve it' for a small fee.

Thankfully, preventing a Conficker infection is easy. Our tutorial shows you just how easy.

But first, we address that rarity of modern malware: one written just for fun. Mikeyy, a worm that attacks Twitter accounts and sends spam Tweets, was written by 17-year-old Michael Mooney because he was bored and wanted to promote his site.

The easiest way not to be affected by Mikeyy is not to use Twitter. If that's not an option for you, read on.

Beat Mikeyy the Twitter worm

1. Twitter users should never click any links in messages containing the words ‘Mikeyy' or ‘Stalkdaily'. This may sound obvious but, if a friend's account is infected, you could receive messages from someone you trust offering advice on avoiding Mikeyy, with a link to a ‘useful article'.

Removing Twitter's Mikeyy worm: step 1

2. It's a good idea to use third-party Twitter desktop clients such as Twhirl or TweetDeck - both work for PC and Mac - and avoid using the web-based version of Twitter. This is especially true for viewing user profiles, because this is where the attack generally seems to originate.

Removing Twitter's Mikeyy worm: step 2

3. As an additional security measure, you can disable JavaScript in your browser. In Internet Explorer, go to Tools, Internet Options. On the Security tab, click Internet, Custom Level. Scroll down to Active scripting and click Disable. Firefox users can use NoScript to stop any unwanted scripts running.

Removing Twitter's Mikeyy worm: step 3

4. If you've noticed suspicious Tweets from your profile that include the words ‘Mikeyy' or ‘Stalkdaily', it's almost certain that your Twitter account has been infected. Make it clear to other users not to retweet (RT) any of the fake messages. Send a Tweet saying your account is infected and asking people not to retweet.

Removing Twitter's Mikeyy worm: step 4

5. Clear your browser cache and turn off JavaScript. Log into Twitter and delete any messages your profile posted that contain the word ‘Mikeyy'. You can turn JavaScript back on so you change your bio and URL and reset the colour scheme of your profile. Also consider changing your password.

Removing Twitter's Mikeyy worm: step 5

6. Once you've completed the steps above, log out of your account. If you wish, you can continue using Twitter via a desktop or mobile client. For the time being, you shouldn't access Twitter through the web interface, unless you're changing your details or deleting a Tweet.

Removing Twitter's Mikeyy worm: step 6

>> NEXT PAGE: Battling Conficker

Prevent, detect and destroy a Conficker infection

1. Microsoft included a Conficker detection tool in a security update it issued in late March. It's important that your copy of Windows is up to date with the latest Microsoft patches. Go to update.microsoft.com/windowsupdate (in Internet Explorer) and turn on Automatic Updates.

Battling Conficker: step 1

2. To stop infected USB sticks or DVDs infecting your PC, disable Autorun. Instructions for all versions of Windows are given at tinyurl.com/akrbm2. As it involves editing your PC's Registry, you should first back up your PC and set a System Restore point. If you're not sure how to back up the Registry, don't do it.

Battling Conficker: step 2

3. Make sure you have up-to-date, reputable antivirus software on your machine. Visit tinyurl.com/PCAsecurityreviews to research security software. You can't cut corners here: free ‘security scan' websites may redirect you to sites that infect you. Scammers have even attempted to spoof reputable reviews sites such as ours.

Battling Conficker: step 3

4. Like many worms, Conficker uses random file extension names to avoid detection - make sure your security software is set to scan all files. This should happen by default; to be absolutely sure, open your security suite's user interface and ensure the correct option is selected.

Battling Conficker: step 4

5. The Conficker Working Group was formed to fight the worm and built the Conficker Eye Chart. This pulls images from three sites that Conficker is known to block and displays them in a box. If they all show up you're in good shape, but if one doesn't display it could indicate a Conficker infection.

Battling Conficker: step 5

6. It's a fast, easy test, but bear in mind that if you're at work and your PC uses a proxy server for web traffic, you might be infected and still be able to see the images. If you can't see the pictures, ensure image loading is enabled in your browser and your web connection is up to speed.

Battling Conficker: step 6

7. Information on how to remove a Conficker infection has been published by security vendors. Symantec, Microsoft (tinyurl.com/85lvwn and tinyurl.com/bzkwy2) and McAfee offer free tools that can verify the presence of a Conficker infection and remove it.

Battling Conficker: step 7

8. A further option is to roll back your system to a previously known good state using System Restore. In XP, go to Start, Control Panel, System, System Restore. In Vista, go to Control Panel, System and Maintenance, System. Click Advanced System Settings, System Restore.

Battling Conficker: step 8