Malvertising  means the use of online advertising to spread malware. This may include computer viruses and other nasty malware that try to hijack your computer or download your confidential information.

Online advertising is largely through advertising networks. You pay for your ad to appear but don’t necessarily which sites it will appear on.

Malvertising is where the scammers inserting malicious adverts into the legitimate advertising networks. Typically this is done by the scammer putting in legitimate adverts for a while then switching to the malvertising ones.

Malvertising is hard to combat because of the complexity of how the advertising networks operate and how quickly ads can be inserted then disappear.

It was estimated nearly 10 billion ad impressions last year were compromised by malvertising.

The identities of those responsible are often hard to trace, making it hard to prevent the attacks or stop them altogether, because the ad network infrastructure is very complex with many linked connections between ads and click-through destinations.

There have been Malvertising attacks against, eBay, answers.com, talktalk.co.uk and many others involving the hacking of various advertising networks.

Don’t automatically trust adverts on respected websites as they may not realise what’s being advertised.

Malvertising is an attack in which perpetrators inject malicious code into legitimate online advertising networks. The code typically redirects users to malicious websites.

Scammers can target users on highly reputable websites, e.g., The New York Times Online, The London Stock Exchange, Spotify and The Atlantic, all of which have been exposed to malvertising.