Want to improve your security profile? Start by eliminating any use of Internet Explorer 6 (IE6). The browser, now almost nine years old, lacks many of today's modern security features, and thus remains a magnet for online attackers.

But according to a new study, as of April 2010, more than one-quarter of all Web traffic still flowed to IE6 browsers. Still, that's an improvement over January 2010, when IE6 handled 34% of all traffic. Those findings come from a report released last week by Zscaler, a cloud security vendor.

There's hope: In the first four months of 2010, enterprises upgrading to IE8 jumped from 6% to 10%, "no doubt driven by high-profile zero-day attacks," according to the report.

Still, the fact that so many people continue to rely on IE6 represents a bigger security problem. "Whether employing black hat search engine optimization tactics, infecting legitimate sites or spreading fake antivirus software, [attackers] are repeating practiced and automated attack techniques that are succeeding with frightening efficiency," said Michael Sutton, Zscaler's vice president of security research, in a statement.

"Not only are attacks getting more and more sophisticated and targeted, but knowledge of them -- such as the big botnets -- isn't making them go away," he said.

Indeed, everyone from security researchers to enterprise IT managers knows all about many of the attacks being used, plus the biggest vulnerabilities, the ongoing threat from malware, and even the names of the big botnets -- Koobface, Monkif, Torpig, and Zeus. Yet, these types of attacks continue to work.

Furthermore, many of these attacks have become highly automated, lowering the barrier to entry for attackers from hard-core hackers to less computer-savvy types, be they script kiddies or organized crime rings. For example, the Eleonore exploit kit for loading malicious code onto websites accounted for 5% of the browser exploits seen in the first quarter of 2010.

Search engine optimization attacks, which place links to malicious Web sites in legitimate search engine results by hiding keywords in pages, injecting links into third-party sites or setting up dynamic doorway pages which serve different pages to different browsers or search-engine spiders are also prevalent.

For example, according to the report, "shortly after the death of popular R&B singer Johnny Maestro on March 24, 2010, we noted that more than 50% of the links within the top 100 Google search results for the term 'Johnny Maestro' were in fact malicious."