Malwarebytes is to start charging $24.95 (£15) per annum for the 'Pro' version of its popular and well-regarded malware detection and clean-up program, ending a period during which the same deal bought a lifetime license.

The firm announced the change in its release notes for the beta of version 2.0, which represents a major overhaul of the program’s interface. The change was necessary for the program to remain “sustainable,” the announcement said.

“As more and more people have come to rely on us for malware protection and cleanup, our costs in bandwidth, hosting fees, infrastructure, salaries of our researchers, QA department, and more have grown immensely.”

“We do have to make money to pay our staff to continue doing what they love, which is fighting malware.”

So, in essence, there will still be a free version lacking some features but anyone who wants to pay for the Pro version will now only be able to buy it on an annual (rather than liefetime) basis. Note: the announcement of the firm's on the website implied that all versions of the software would be charged for (in effect, abandoning the current scanning-only free version) but Techworld understands that this is not the case.

Licenses already granted on a ‘lifetime’ basis will continue to be honoured on that basis, Malwarebytes confirmed. Furthermore, users paying the subscription fee will be able to run the software on up to 3 PCs.

Despite the annual fee, many of its fans will probably be willing to pay up to get a feature set that includes the ability clean up many malware infections after the event, something conventional antivirus programs lack. It can also quite happily be used as a compliment to a second antivirus program without the risk of memory clashes.

Other features included a complete rewrite of the detection and removal engines, improved malicious website blocking and more 64-bit code.

“We could have gone other routes to make our business more financially sustainable, like adding toolbars or advertisements like many other security products have, but that's not the company we are. We believe that products should be nag-free and cleanup shouldn't cost our users a dime, and we're going to stay true to that,” Malwarebytes said.

Malwarebytes slowly expanded it family range during 2013, launching a version of the program for small business users that embedded the scanning engine on a USB stick; on that topic, the business-oriented version of version 2.0 will be available in "a few months," the firm said. It also now offers a cloud backup system that incorporates scanning for malware as files are transferred.

Last summer it bought out a stealth startup, ZeroVulnerabilityLabs, founded by fomer Panda Security engineers.