Definition - What does Cookie Theft mean?
Cookie theft occurs when a third party copies unencrypted session data and uses it to impersonate the real user. Cookie theft most often occurs when a user accesses trusted sites over an unprotected or public Wi-Fi network. Although the username and password for a given site will be encrypted, the session data traveling back and forth (the cookie) is not.
Techopedia explains Cookie Theft
By mimicking a person’s cookie over the same network, a hacker can access sites and perform malicious actions. Depending on the sites accessed while the hacker is monitoring the network, this could be anything from making false posts in that individual’s name to transferring money out of a bank account. Hacking software has made it easier for hackers to carry out these attacks by monitoring the packets going back and forth. Cookie theft can be avoided by only logging in over SSL connections or employing HTTPS protocol to encrypt the connection. Otherwise, it is best not to access sites over unsecured networks.