Information leakage

Information is all around us. We don't even realize how much information we share with everyone, and I have two examples to think about.

Business cards
We use to give away our business cards to colleagues and potential customers without realizing how much people can learn about us.
We put our mobile phone number, so now people can reach us 24/7.
We put our phone number, something such as 917-999-6666 and now the potential attacker knows that most of our company phone extensions (and maybe our fax and modem lines) begins with 917-999xxxx and that our extension is probably 6666 (wonder whom will I reach trying 6665 or 6667...)
We put our fax number, which can be used by spammers and advertisers we once met at a commercial fair.
We put our email address, something such as johnd@somecompany.com (in most cases, our username to the internal company assets will be something such as Johnd)

Voicemail / out-of-the-office message
We tend to leave a message on our voice mail or on our company mailbox, information such as:
"Hi, you've reached John Doe, from the sales department. I will be out of the office between July 28th and August 2nd. In case of emergency, you may contact Linda Smith, at 5435742, ext. 2"
If I was a potential hacker, I now know that John will be out of the office, I know his department name, I know the dates he will not be available, I know who replaces him while he is out of the office, and I know how to reach her.
Instead of giving away all this information, why not use something polite and simple, such as:
"Hi, I will be out of the office. You may send me emails and I will get back to you as soon as I will return to the office."

Think about it, the next time you share information, and don't forget that everyone on the internet can see it, the next time you share photos from your wonderful vacation on facebook, or what a great day you had, on twitter, just after you told your boss, you are not coming to the office today since you are not feeling well.