The story of a pair of successful hackers highlights the targeted, sophisticated attacks that are now taking place and the defenses that companies can put in place to protect themselves. Michael and Ruth Haephrati wrote a Trojan horse, a type of software that sends information from the computer system it infects back to the hacker that put it there. The email messages they sent appeared to be a business proposal from a company their victims would trust. David Cole, director of security response at Symantec Corp, says that employees should be trained to recognize the signs that malicious software has been planted on a computer. Specifically, employees should watch for unusual behavior by their computers when they open an attachment such as error messages, crashing applications, the sudden appearance of windows, or a slowing down of the system. Once the Haephratis' Trojan was installed, it scoured the computer for sensitive information. Luckily, more sophisticated security software is available today that is able to detect programs that are similar in some way to past attacks. Business should keep their security software (from vendors like Symantec, McAfee Inc. and Trend Micro Inc.) up-to-date. Intrusion-prevention systems can limit harm done even if a business's security software fails to detect a break-in. Cisco Systems Inc., Jupiter Networks Inc. and International Business Machines Copr. all sell intrusion-prevention systems.