AT&T Corp. T.N has warned employees not to be tricked into surrendering sensitive information about its network to hackers posing as colleagues or customers this weekend, a spokeswoman said on Friday. The warning, sent in an e-mail to AT&T staff, came ahead of a major hackers convention in New York where some of the attendees plan to give a demonstration of “social engineering” techniques — ways of getting information that can be used to break into computer networks from the people who run them. Full Story