Those who would later phish on AOL during the 1990s originally used fake, algorithmically generated credit card numbers to create accounts on AOL, which could last weeks or even months. After AOL brought in measures in late 1995 to prevent this, early AOL crackers resorted to phishing for legitimate accounts.
Phishing on AOL was closely associated with the warez community that exchanged pirated software. A phisher might pose as an AOL staff member and send an instant message to a potential victim, asking him to reveal his password. In order to lure the victim into giving up sensitive information the message might include text such as “verify your account” or “confirm billing information”. Once the victim had submitted his password, the attacker could access and use the victim’s account for criminal purposes, such as spamming. Both phishing and warezing on AOL generally required custom-written programs, such as AOHell. Phishing became so prevalent on AOL that they added a line on all instant messages stating: “no one working at AOL will ask for your password or billing information”.
After 1997, AOL’s policy enforcement with respect to phishing and warez became stricter and forced pirated software off AOL servers. AOL simultaneously developed a system to promptly deactivate accounts involved in phishing, often before the victims could respond. The shutting down of the warez scene on AOL caused most phishers to leave the service, and many phishers — often young teens — grew out of the habit
Source : wikipedia