Microsoft has started classifying most versions of the Ask Toolbar as unwanted software and has updated its malware programs to automatically remove them.

The move drew applause from security and support professionals because the Ask Toolbar has long been a source of performance problems that can sometimes be hard to correct. Making the toolbar more vexing is its ability to sneak its way on to computers when end users aren't paying attention. Oracle's Java software framework, for instance, has long installed it automatically unless users remember to uncheck a hard-to-see box during updates. Even after unchecking the box during one update, the box would be checked during subsequent updates, requiring end users to remain vigilant each time they installed frequent security fixes for Java.

In a recent addition to Microsoft's Malware Protection Center, the company said all but the most recent version of the Ask Toolbar will be classified as unwanted software. As a result, Windows Defender, Microsoft Security Essentials, and Microsoft Security Scanner will automatically remove it when detected.

"This software poses a high threat to your PC," Microsoft's recent entry warned.

Microsoft hasn't said exactly why the toolbar is being banished or why the move is coming only now. The list of criteria for determining what is unwanted software covers unwanted behavior, the delivery of unwanted advertising, a loss of user privacy, and input from end users. In a blog post published two weeks ago, Microsoft officials said they were going to get tough on apps with search protection functionality, meaning those that take control of a browser's search functionality. In April, Google began cracking down on Chrome browser extensions after classifying many of them as malicious.

Update: A spokeswoman for the Ask Toolbar developer said Microsoft's move banishing older versions affects less than one percent of the toolbar's user base.