Why banking websites always ask me to authenticate my PC even after I'd chosen to Remember my PC? This is the case with all banking websites
migrated from superuser.com Oct 31 '11 at 23:24
An aspect of security which more and more banks are implementing is to try not to trust anything sent by a computer, as an attacker could theoretically change the responses sent to the bank.
Imagine you have authenticated your PC, and an attacker has captured your traffic and has your cookies. If they then try to log on to your account and the bank doesn't ask them to authenticate their PC, that is one less hurdle for them to beat in order to get at your money. So the bank can insist that their cookies are not stored, or that specific ones are wiped on logout.
From a general security perspective, I wouldn't let my PC remember any details from an internet banking site, or in fact any site that could be used to steal sensitive usernames or passwords.
Financial institutions use patten recognition to 'remember your computer'.
It is similar to licensing schemes where a software license is locked to a specific computer.
Some input that they use to determine identity on your computer is likely not static.
It coule be: a browser cookie, your IP address, the MAC address of your ethernet or WiFi card, your username, the amount of available RAM in your computer, your hard drive serial number, your motherboard model, the id value of your CPU, your operating system version, or any one of a number a things that a financial instution might believe would not chaange on most customer's computers, but does on yours.
It remembers you, but it's double-checking to make sure it really is you.
When you click "Remember my PC", it puts a cookie on your computer that remembers your session. However, your current privileges of the session timeout. For example, once you've entered your password, you can probably check your account balance for days. But after a few hours, if you try to withdraw money, you'll have to re-enter your password. That prevents you from walking away from your computer, and having somebody else walk up and withdraw money.
Likewise, if you go to account settings, you can view your mailing address, but if you try to change it, the site will yet again ask you to authenticate.