There is a fake AT&T online bill e-mail message that contains links to a malicious website. If you click on any of the links in this e-mail message, you will be redirected to a malicious website that uses the Blackhole exploit kit to infect your computer with malicious programs (malwares).
The Blackhole exploit kit is currently the most popular web threat, where it is used to deliver group of malicious programs to the victim's computer.
For more information about the Blackhole exploit kit, please go to http://en.wikipedia.org/wiki/Blackhole_exploit_kit .
Here is a copy of the fake AT&T bill:

My ATT Account
Your online bill is ready to be viewed
Dear Valued Customer,
A new bill for your ATT account is ready.
Any payments completed after your bil period expires will not be shown in the bill amount listed
direedy below. If you have made a recent payment, please refer to the current balanoe on the
Account Overview and the Bill Q Payments pages.
Log in to online account management to view your all and bull notices, maintain your email
account or make a payment. If you are not reoistiered for online account management, you
must do so to view and print your full bill and bils notices at www.att.com/managemyaccount.
Log in to online account management to view your bill, maintain your email account or make a
payment.
Thank you for choosing ATT. We value your business and look forward to serve you!
Thank you,
ATT online Services
www.att.com
Although the e-mail message looks legitimate, do not open, click on any attachment, visit any links in it. Delete the e-mail if it ends up in your mailbox.
To login into your ATT account, please enter http://www.att.com in your browser's address bar and login when the page loads. The login box is on the right side of the page.