The new Apple iPhone OS 3.1 software comes with a new anti-phishing feature for the Mobile Safari browser, but researchers say the filter doesn't work.

"I've not been able to get it to block anything," says Michael Sutton, vice president of research at Zscaler, who has been testing the mobile browser's security feature against several phishing sites identified on PhishTank. While Apple's Safari for the desktop blocks many of the sites, the iPhone's mobile version didn't block any that he tested.

Sutton says it's either a bug in the OS 3.1 software, or the new iPhone software just runs a pared-down version of the Safari browser's security feature. "OS 3.1 has settings in the Safari browser for turning on and off phishing protection, but it's just not [working]," Sutton says.

Apple had touted the new iPhone OS 3.0's anti-phishing feature, but Sutton says the feature was a no-show once the software was released in June, and he assumed the feature had just landed on the cutting floor.

Meanwhile, The Mac Security Blog is also reporting problems with the iPhone's anti-phishing feature, which is supposed to warn users when they visit a known malicious Website and ask them if they want to continue. "We have extensively tested this feature, tossing dozens of phishing URLs at it, and it simply does not seem to work. URLs that are blocked by Safari in Mac OS X open and direct users to malicious pages," they wrote.

Meanwhile, The Mac Security Blog says some people who have tested the feature have reported that it works for them, while others say it's not working. "We've tried isolating locations, iPhone/iPod touch models, and whether they are connecting over a cell network or via wifi, but all we've come up with is that sometimes it works and sometimes it doesn't. This is clearly more dangerous than no protection at all, because if users think they are protected, they are less careful about which links they click," they blogged.

"If two people go to the same phishing site [and only one gets warned], there's clearly something wrong here," Zscaler's Sutton says.

Apple has been under fire for the barebones antivirus feature it included with Snow Leopard, its new version of OS X, which security experts say is inferior to available AV offerings.

Zscaler's Sutton says the fact that Apple attempted to secure the mobile browser is a plus: "On one hand, I'm encouraged," he says. "It's been an issue of mine for a while that mobile browsers don't have security built in."

But the worry is that since Apple is selling the new iPhone OS as having a phishing protection feature and it's not working, iPhone users are getting a false sense of security. "I applaud them for being the first to try to implement security features," he says. "But it appears they didn't do it right."

Apple had not responded to a request for comment on the issue as of this posting.

But even if the iPhone browser's anti-phishing feature was in working order, it couldn't stop a targeted attack, says Joshua Perrymon, CEO of PacketFocus. "What the browser will do is alert on known phishing attacks that are blacklisted, along with limited heuristics to identify other phishing attacks. It will do nothing for directed, custom attacks -- and these are the most damaging to an organization because most are never detected," Perrymon says.

"Also, mobile email is a great target for attackers because of this limited protection. There may be a small chance that desktop software may identify a phishing attack, but current mobile smartphones aren't really protected at all," he says.

Perrymon says while anti-phishing is a "good idea" for the iPhone, don't expect such a feature to protect users against any "real" attacks.

Have a comment on this story? Please click "Discuss" below. If you'd like to contact Dark Reading's editors directly, send us a message.