Corporate cyber attacks on the rise.

According to two new surveys, the threat to corporate computer systems from worms, viruses, and cyber attacks is getting worse, despite stronger corporate defenses. The data show that although corporate America is getting smarter and more aggressive about defending its networks from attacks, criminals are also getting smarter and more aggressive in their attempts to defeat them.

A recent study by security software provider Symantec found the number of "phishing" attacks--when individuals try to fraudulently obtain passwords and sensitive personal information through official-looking email messages--skyrocketed more than 260 percent in the second half of 2004. Virus and worm attacks against Windows-based computers jumped more than 300 percent. The number-one target for these attacks was financial institutions.

A survey of 229 mid-size and large companies conducted in January by network security firm Mazu Networks found that 47 percent had networks that were hit by a self-propagating worm in the past year.

Experts say cyber attacks are now trying to bypass companies' traditional defenses. So even though companies may be improving their peripheral defenses, cyber criminals are working on attacking through individual computers or a browser--avenues that are more difficult to protect against.

Security experts say flaws in Microsoft's Internet Explorer are partly responsible for the increase in cyber attacks. And companies that rely heavily on mobile computing through wireless devices and offsite contractors are becoming more vulnerable to computer break-ins. In addition, companies are opening up their networks to improve efficiency and performance and enhance connectivity, giving criminals more access to their internal networks, experts say.