Websites that require registration often have a checkbox the user can tick so that they will not have to re-enter their username and password on subsequent visits. The text might state “remember me on this computer,” or words to that effect. Just what happens when you check this box, and how safe is it to do this?

Providing the Web browser is configured to allow cookies, when a user elects to “remember me on this computer” the website creates a cookie with the user’s registration information. A computer cookie is a small text file that resides on the user’s machine with a copy filed on website’s server. Think of it as a nametag with a few more bits of information. The next time the user visits the site, the browser automatically hands over the cookie upon arrival. The website allows automatic entrance because the Web browser has essentially handed it your credentials.

In many cases this is fine. For example, if the website is a TV chat forum, syndicated newspaper or clipart website, there is likely no harm in it. However, if the website holds personal information about you, choosing to “remember me on this computer” is probably a bad idea.

Online banking, Web email accounts and online retailers are all examples of websites where you probably do not want automatic admittance. If anyone uses your computer and visits the site (probably easily found in your bookmarks), he or she will be automatically logged into your account. This will give the ‘imposter’ instant access to private information including potential bank records and finances.

Assuming everyone in your household is trustworthy (you might even live alone), there is still reason to avoid ticking the “remember me on this computer” box. It might happen that you need to drop off your computer for repair, that it’s stolen, or that visitors ask to use the computer. This is especially true of terminals at work. Automatic logon to sensitive sites can put you at unnecessary risk.

For maximum protection it is best to reserve “remember me on this computer” for sites that do not hold personal information. If you have trouble remembering logon information there are programs designed to hold your usernames and passwords for you in encrypted form. Two such programs are KeePass Password Safe and Secure Data Manager, which are free and open-source. Open-source programs make their source code publicly available online so that it can be widely checked for bugs and security flaws.