Microsoft Internet Explorer 8 Beta 2 will put a bull's-eye on malicious sites courtesy of the new SmartScreen Filter.

The feature, revealed July 2, is an answer to the blacklisting features built into Firefox 3 and Opera 9.5, and builds on the Phishing Filter introduced in IE 7 with, among other things, anti-malware support and new heuristic detection capabilities to block known bad sites. Security has been a key battleground between Microsoft's Internet Explorer, Mozilla's Firefox and other browsers. In addition to blocking bad sites, the filter also protects users who click on a link leading to a download on a rogue site by interrupting the download with a warning, according to Microsoft.

When it comes to thwarting XSS (cross-site scripting), Microsoft has added a filter that uses a heuristics-based approach to sanitize injected scripts.

"The XSS Filter operates as an IE 8 component with visibility into all requests [and] responses flowing through the browser," David Ross, a security software engineer at Microsoft, said in a blog post. "When the filter discovers likely XSS in a cross-site request, it identifies and neuters the attack if it is replayed in the server's response. Users are not presented with questions they are unable to answer—IE simply blocks the malicious script from executing."