Java flaw poses security risk to Windows, Mac and Linux

Windows, Mac and Linux users are being warned of a dangerous Java flaw that could pose a threat to home PCs.

Security firm Websense confirmed that although the size of the attack is currently small it is likely to become serious very quickly. This is because criminals are using the popular Blackhole kit to use a vulnerability in Java 7, the latest update to Oracle's software, to install a banking Trojan on a PC.

How to disable Java

It is believed up to 3 billion PCs may have Java installed but few people update or patch the software and there is currently no fix for this vulnerability.

The situation is becoming so serious that security experts have already called for people to disable Java (which should not be confused with Javascript), because criminals are increasingly using vulnerabilities in this third-party software to spread malware.

Read more: Java guides | security tips

The company warned it has also intercepted a malicious email campaign posing as anti-virus notifications that warn users that their accounts may be blocked.

These fake messages, which carry the name of big security software companies such as Norton and Sophos, state that the victim's email address has been sending infected email to the mail server, and that the situation may be remedied if the user clicks a on a link to download a free removal tool.

"The free tool is, of course, a malicious executable that connects to malicious websites, and then drops more executables on the victim's computer," warned Websense.