"Zero day" was the mantra for attackers in 2006, and the trend shows no signs of letting up next year, according to a new report issued by The SANS Institute earlier today.

In its annual, in-depth study of the Internet's most popular online exploits, the security research and training organization found that zero-day attacks have skyrocketed over the past year.

"In 2006, we've seen a significant rise in attacks that take advantage of zero-day vulnerabilities, leaving a user or system unable to defend against the attack, since there is no patch available," says Marc Sachs, director of the SANS Internet Storm Center and SRI International.

The interest in zero-day exploits is increasing as companies and end users improve their patch management, says Rohit Dahmankar, senior manager of security research at TippingPoint Technologies Inc. "As automated patch management has emerged, we've seen greater interest in zero-day attacks," he says.

Microsoft Corp. (Nasdaq: MSFT) applications, particularly Office programs such as Excel and PowerPoint, are a key target for these attacks, Sachs says. Such application-level attacks often circumvent traditional security defenses such as firewalls and IDSs, and usually aren't handled by antivirus tools. "This fact is well known to the criminal and espionage communities, and is one of the key reasons for the rapid growth of this attack methodology," says Dahmankar.

Qualys Inc. , a security vendor that has been tracking attacks on the Microsoft suite, has seen a threefold increase in instances of attacks on those applications in the last year, according to Amol Sarwate, manager of Qualys's Vulnerability Management Lab. "About 20 percent of those attacks were zero-day," he says.

Many of the zero-day attacks on Windows applications are initiated in China, according to Sachs. The country's lax position on intellectual property rights makes it relatively easy for attackers to get access to Microsoft source code, and there are few law enforcement agencies investigating such attacks on other countries, he observes.

Attacks on U.S. military and government sites are also on the rise, according to the SANS Institute report. A U.S. Air Force general recently conceded that "petabytes" of its data had been stolen by foreign governments, and that the Department of Commerce recently announced plans to replace hundreds of computers because of security vulnerabilities, according to Alan Paller, director of research for the Institute.

Voice over IP technology has also become a popular target for attackers, the SANS experts say. "The FBI reports that many VOIP systems are being compromised so that criminals can sell minutes and leave the bill with the victim," Dhamankar says. Federal authorities broke up such a scam in June. (See Two Charged in VOIP Hacking Scandal.)

Dhamankar also expressed concern that attackers might use VOIP servers to inject bad messages into the public switched telephone network. "We haven't seen it happen yet, but with the interconnection of VOIP servers and traditional SS7 systems, it's possible," he says.

Another popular attacker target is the Web application, says Johannes Ulrich, CTO of the SANS Internet Storm Center. "Web applications have become an Achilles heel for a lot of enterprises," he says. "In many cases, the business is forced to keep its interfaces open, which leaves it exposed to attacks."

Attackers are targeting Web applications not only to steal data, but to use highly-trafficked Websites to launch other types of browser attacks, Ulrich observes. Other experts have pointed out that most enterprises still have a lot of work to do on Web application security. (See The Web App Security Gap.)

— Tim Wilson, Site Editor, Dark Reading