Microsoft has ended technical support and security updates for older versions of its Internet Explorer browser.
The changes, which will affect versions 8, 9 and 10 of the browser, were announced in August 2014.
Some estimate that these older browsers account for more than 20% of web traffic while Computerworld claims that only 55% of IE users are using the latest version.
Browsers are often targeted by hackers and experts predict a crop of attacks.
“Beginning January 12, 2016, only the most current version of Internet Explorer available for a supported operating system will receive technical support and security updates,” the software giant announced on its website.
“Microsoft encourages customers to upgrade and stay up-to-date on the latest browser for a faster, more secure browsing experience.”
It is continuing to support IE 11 and Edge, which is the default browser for Windows 10.
NetMarketShare estimates that Internet Explorer accounts for 57% of the browser market, compared with 25% for Chrome, 12% for Firefox and 5% for Apple’s Safari.
According to Computerworld, some 340 million people still rely on older versions of the IE browser.
It has led security experts to warn of a security “hot potato”.
“It is safe to assume that cybercriminals have been stockpiling IE vulnerability information ahead of the support cut-off,” said Craig Young, a researcher at security firm Tripwire.
Mark James, researcher at security firm ESET added: “No updates, no patches, no fixes, no new versions and no support options if things go wrong. This basically means it’s a hot potato and you need to drop it as fast as you can.”
Microsoft has been warning users to upgrade for some time but some believe that it has had the reverse effect – drawing users to rival browsers such as Firefox and Chrome.
In April, Microsoft officially stopped security support for Windows XP and while many envisioned a malware explosion it did not materialise.