A malware attack is being spread via Twitter using "zombie" accounts to push a site which claims to link to a fun video.

Using the tagline "haha this is the funniest video ive EVER SEEN!", and a wide variety of Twitter hashtags, the website instead uses a Java exploit to drop a keylogger program and a banking Trojan (which will search your hard drive for any banking details and watch when you log in to online banking sites) on Windows computers that visit it.

The large number of accounts are being used to try to push the link onto trend-mapping sites that show popular links on Twitter.

F-Secure spotted the emergence of the threat today, and explained how it works. And it had a suggestion for how to avoid the problem: "Lesson of the day is probably this: do you really need Java in your browser?" asks the company. "Seriously, do you? If not, get rid of it."

The breadth of the attack indicates that the linked problems for Twitter - that it doesn't seek any authentication of accounts beyond an email - and URL shorteners, which can make it hard for people to know where they are going mean that users of these services have to be cautious when using Windows systems.

Bit.ly has been alerted to the threat from the link; presently its statistics indicate that there have been more than 1,630 clicks on the link - each of which means an infected computer and someone whose banking details are therefore at risk, and whose computer is a potential spam generator and botnet member.

If you have clicked on the link, you should immediately take your machine offline and scan it with an antivirus system.

If you need to check the final destination for a bit.ly URL, it's easy with bit.ly links: add a + to the link you're offered (eg http://bit.ly/b6Z3BC+, which shows the statistics for the URL for the dangerous site).

Other URL-shortening services can make it harder to check where you're being sent. Tinyurl offers a "preview" function, but it's always wise to look at any available information before continuing to a link from a source you don't completely trust.