A recently disclosed fraud involving hundreds of thousands of people on the Monster.com jobs Web site reveals the perils of leaving detailed personal information online, security analysts say.

Before the scheme was uncovered last week by researchers at Symantec Corp., con artists had filched legitimate user names and passwords from recruiters who search for job candidates on Monster. Then with access into the Monster system, the hackers grabbed resumes and used information on those documents to craft personalized ''phishing'' e-mails to job seekers.

''What phishers are trying to do these days is make them as realistic as possible, by adding specific information,'' said Patrick Martin, a Symantec product manager. ''If they know you've submitted a resume to Monster, that makes it (seem) a little more legitimate.''

If the recipients took the bait, they had spyware or other malicious programs secretly installed on their computers. But even if the phishing attempt wasn't successful, the names, addresses and other details on the resumes can themselves be lucrative.

A server in the Ukraine used in the scheme held 1.6 million entries. Because of duplications, Symantec said those files actually held personal information for ''several hundred thousand'' job seekers. Another antivirus firm, Authentium Inc., said it parsed the same data and counted 1.2 million people.

Symantec said it relayed details to Monster.com so it could disable the compromised recruiter accounts. But the security company also advised Web users to limit their exposure to such frauds by reducing the amount of personal information they post on the Internet.

That advice was echoed in other corners. Ron O'Brien, senior security analyst for Sophos PLC, suggested that job seekers provide only minimal details about themselves on job sites, and then reveal deeper information only for queries that prove to be legitimate.

The same standards should apply on social networking sites such as Facebook that ask for a wealth of information, O'Brien said.

''With very little effort, I could put together a profile of you that includes such information as your home address, your home phone number, your e-mail address, your birthday,'' O'Brien said. ''We need to kind of take a step back and decide whether it's really required for us to provide all the information requested of us. ... We have become a nation of people who want to be cooperative.''

Other security specialists said Monster might share the blame if it doesn't ensure that people with access to its system use ''strong'' passwords that are frequently changed or hard to guess.

''They have a major responsibility when they have this information,'' said Laura Yecies, a vice president of Check Point Software Technologies Ltd.

Representatives for Monster Worldwide Inc., the New York-based parent company of the jobs site, did not return messages seeking comment.

On its Web site, the company advises its members to be extremely cautious about e-mails purporting to be from recruiters - advice that goes for all unsolicited messages.

To spot phishing attempts, look for misspellings or grammatical mistakes in the messages. Even if an e-mail passes that smell test, don't click on links in the e-mail or fill out forms asking for information. And if the message offers a deal that is too good to be true - such as easy money - it probably is.