According to The Register then Older versions of the Ask Toolbar are now considered Malware by Microsoft:
In a June 11 update to its Malware Protection Center site, Microsoft states that older versions of the toolbar, which set itself up as a browser's homepage and redirected all searches through Ask's engine, now contravene Redmond's policies. The latest build is fine, but older Ask toolbars will be hunted down and deleted.
"Older versions of software can restrict or limit your control over your search provider. It can prevent you from disabling or modifying your search provider," said Microsoft's advisory. "This software poses a high threat to your PC."
[...] The bulk of this comes thanks to Java, because for years every Java update for PCs asks if the user would like to install Ask's toolbar. Many a computer user has unthinkingly clicked through and installed the toolbar. Those running Java on OS X have been getting the same opportunity to experience the joy that is Ask's toolbar since March.
Also reported at PCWorld and Geek amongst others.
However as pointed out by the Register this may only affect older versions:
Ask confirmed to The Reg that its current toolbar is "fully compliant with Microsoft policies" and that its software should automatically update to the latest version every time the browser is opened. A spokeswoman said only one per cent of Ask's user base is affected by the change.
(Score: 0) by Anonymous Coward on Saturday June 13 2015, @10:12PM
I can't help it if Windows Defender tells me that Windows is a virus, after all, they should know.