Like their medical counterparts, a computer virus’s lifespan is determined by how effectively it spreads from machine to machine. And, like its biological counterpart, there are things you can do to avoid leaving yourself wide open to infection.

Computer viruses do have quite a few tricks up their digital sleeves, but it always pays to know the ways in which a virus spreads itself, so you can protect your computer at the first sign of trouble.

1) Networks
It’s hardly fair, but with most offices and homes running networks these days all it takes is for one person to get a virus and soon they’ll be sharing it around. There aren’t really any ways to avoid viruses spread this way, but if you make sure everyone’s anti-virus settings are up to date, you can minimise the pain of quarantine and removal.

2) Infected software.
There’s so much free software available on the Internet today, but sometimes it isn’t what it seems. Sometimes you can find that, alongside a real installation, adware or other malicious software is being installed. Keeping your anti-virus protection up to date will help, as will keeping a wary eye about you when you are looking for software. Choose reputable websites and programs with an established following, and you’ll be minimising your risk.

3) Email Attachments.
Back when the Internet was young and innocent, email clients used to open attachments automatically. You won’t find them doing that any more, but attachments in email are still one of the most common methods of transmission. A simple golden rule is that if you don’t know what it is, and you weren’t expecting it, then don’t open it.

4) Mobile devices.
Nowadays, everyone has things plugging into their computers; cameras, phones, external hard drives, USB drives, etc. But any of those could be carrying a virus, and worse, many of them have auto-run installers designed to make the user experience easier. Switching off the auto-run facility on your computer will help, as will scanning your device every time you move it from one machine to another.

5) Hackers.
These days, the risk from hackers is low – most people know to use a firewall to protect themselves from incoming attacks. However, it is still important to keep your firewall and anti-virus updated, as allowing your protection to lapse is like rolling out the welcome mat.

6) Instant Messenger.
Instant Messenger and chat software is one of the great chinks in the armour of online protection, as it can leave computers open to hacker attacks. However, a bit of common sense can keep risk to a minimum. Restrict your chatting to a circle of friends and try not to click on links and downloads, and you should stay safely protected.

7)  Rogue Websites:
Not all websites are what they claim to be. Certain websites containing adult material, or those that offer gambling, try to gain access to your computer while you’re browsing, sometimes doing as little as opening a flurry of unwanted pop-ups, others installing more malicious software at the same time. Playing safe and using your common sense can minimise your risk, along with keeping your anti-virus protection up to date.

8) Fake anti-virus software.
To add insult to injury, you thought you’d try a new anti-virus which promises maximum protection. Instead your PC is riddled with viruses. The best way to avoid this pitfall is to do your homework – if you want new anti-virus software, do some research and find yourself a reputable piece of software with an established track record.

9) Friends and Family.
It’s frustrating, but you can’t expect everyone to be as careful as you. If a relative or friend sends you an email attachment, or brings their holiday photos over on a USB drive, it can be hard to remember your anti-virus security. However, a little vigilance will help make sure you never inadvertently download a host of viruses along with Aunt Mabel’s trip to America. Keep your anti-virus up to date and scan everything you plug in.

10) Phishing Schemes.

Phishing is a relatively new problem. Knowledge is power, and phishing attacks are an attempt to collect personal information to carry out identity fraud. The most common phishing scheme is when an email arrives pretending to be from your financial provider. You’ll be asked to click a link and log in, at which point your personal information will be in the hands of the phisher. On top of this, the site may well have downloaded viruses and annoying adware to your computer.

These ten are some of the most common ways you can get computer viruses, or be exposed online. You can save yourself from a lot of them by staying smart, having your wits about you, and keeping your antivirus updated and your online protection chink-proof.

Written by Alex Johnson, a blogger on internet security issues.