Systems and methods for creating and analyzing computer tag information for the prevention or detection of potential fraud. Computers and other devices accessing the Web carry device tags with date and time information describing when they were issued by a security tag server. A server time stamp may be inserted into time based computer tags such as a cookies indicating when they were created. Such time stamp information can be encrypted and analyzed during future attempts to access a secure network such as a customer attempting to log into an online banking account. When the time stamp information from the tag is compared to other selected information about the user, device and/or account, including but not limited to last account log-in date/time or account creation date, the invention may be used to detect suspicious activity.