In a preceding column, I discussed controls over the information posted in the WHOIS database for DNS registration, pointing out that it is unnecessary to give specific employees\u2019 names and phone numbers in that database. I\u2019d like to continue on that theme with some warning about other ways we tend to reveal too much about ourselves and our activities in today\u2019s electronically interconnected world.Let\u2019s start with e-mail. Why give away information that is unnecessary for most correspondence yet valuable for social engineering? In your signature block, is it necessary to post your complete physical address, including precisely which building and office you work in?\u00a0 If someone needs to visit you, you can give them your precise location details once you have established some basis for trust. Do you have to give your secretary\u2019s name and phone number? What about your fax number - why invite junk fax? If someone needs to send you a fax, they can ask for the number.When you are going away on a business trip or a vacation, is it really to your advantage to broadcast exact details of when you will be away, why and where? Doesn\u2019t this information provide easy ways to impersonate you or to take advantage of your absence for robbery, data theft, sabotage or other types of harm? And remember that auto-replies are always dangerous: All you need is a message to be sent by someone who happens to turn on their own out-of-office auto-reply and you have a mailstorm brewing. Your autoreply sparks their autoreply which sparks another autoreply from your mailbox and so on until a server crashes or someone notices the flurry of useless e-mail.Think now - when you leave your home for a vacation, you do not put a big sign on your front lawn that reads, \u201cWe\u2019re going away for two weeks now, so there\u2019s no one home and you can rob us blind or burn the house down more easily.\u201d No, on the contrary, you arrange to stop newspaper and milk delivery so that there are no telltale signs of your absence; you may set automatic lights to go on and off; you arrange with your neighbor to water the plants and pick up regular mail - all to avoid announcing to Bad People that you aren\u2019t at home.So why do the opposite at work? Are you really so important that every single person sending you e-mail absolutely has to know that you\u2019re away? Why not let the ones who really care simply call your work number, fall back to the backup person who answers in your place, and learn a limited amount about your absence as required? While we\u2019re on the subject, apply the same reasoning to your voice-mail messages. \u201cI\u2019ll be away until next week\u201d may make you sound important, but it may also invite theft or spoofs.As for the Web, just because it\u2019s easy to post information doesn\u2019t mean that all of it should be posted. For example, on a personal Web site, some people post - I\u2019m not kidding - their date of birth and their Social Security number. Resum\u00e9s (CVs) can be so detailed as to provide the basis for successful impersonation; necessary? On corporate Web sites, some organizations post detailed internal phone lists with employee names, titles, departments, office numbers, phone numbers, fax numbers, secretaries\u2019 names - the whole shebang. Maybe a bit too much, no? Some companies post excessively helpful competitive information such as detailed lists of important clients; what better help to competitors could one ask for? And some organizations cheerfully post internal documents such as minutes of meetings, strategic plans, and competitive analyses on their public Web sites, perhaps under the mistaken impression that these are the same as their private intranets.I hope that this litany of openhearted, trusting publication of information has sent some premonitory chills up the spines of some readers. Perhaps there will be a flurry of activity as readers rethink just how much information really ought to be made public in their e-mail and Web sites.Isn\u2019t it awful being so suspicious?Isn\u2019t it worse not being able to be suspicious on demand?