Corporate executives should think twice about the information they disclose on social networking sites such as Facebook, a Hong Kong-based security company warned Friday after duping gullible CEOs and finance directors into revealing personal details that could be used for so-called spear-phishing attacks.

Network Box, which makes and sells threat prevention appliances, recently conducted an experiment to see how difficult it is to glean important information from business executives.

"We were asked to see if we could gain information about individuals without having a real-life link to them," said Simon Heron, Network Box's managing director, in an e-mail. "We used a fake Web mail account to create a fake Facebook account. With this, we approached individuals who we knew to be in quite senior positions and simply asked to be their friends, explaining that we knew them while at school."

The results would make an identity thief proud. Several of the targets, explained Heron, gladly accepted the request from the bogus "friend," giving Network Box access to their profiles, which in turn could be mined for the kind of personal information necessary to make very targeted phishing e-mails convincing.

"We found personal details, including dates of birth, mobile phone numbers, home addresses, company name and job titles, and even [a] mother's date of birth," said Heron. "If [you] wanted to go spear phishing, knowing your prey has money is key, as well as how to target them. If you know they are a CEO or [finance director], then you know they will be vulnerable about getting complaints about the company. We can then target them to download documents with malicious code embedded or get them to visit an infected site."

Criminals will go to great lengths to obtain the information they need to craft a spear-phishing attack, if only because the targets -- high-profile company executives who have access to a firm's most important secrets or data -- are so lucrative. One of the most egregious examples of spear phishing in the last year was the follow-on spam campaign that cybercrooks launched after looting Monster.com's database, making off with information on 1.3 million people who had posted resumes on the popular job search Web site.

Heron recommended that executives steer clear of all social networking sites, and that companies remind all employees to refrain from posting company information on such places.

"Any con can be a lot more successful if the con artist has personal information about the target," Heron concluded.