Chrome, Firefox and Safari all use the same data feed of malicious URLs -- Google's Safe Browsing, which explains why their overall protection ratings are similar, the report says. Supporting this notion is that results for the three browsers rose and fell in unison over time.

The testers noted that Opera would detect a malicious site sometimes, but later would miss it. That could be attributed to the fact that in some cases the warning that a site was malicious would pop up after the malware had already downloaded or even downloaded and executed, the report says.

In general, users are four times more likely to be socially engineered into downloading malware than they are to fall victim to a software exploit.

in Network World's Wide Area Network section.