Terms related to pharmaceutical drugs and phishing scams topped the list of the most widely sent junk e-mail subject lines used by spammers this year, AOL said.
Phishing, the use of faked emails to get internet users to reveal passwords, credit-card numbers and other information, rose to number two and three on the list, reflecting a significant increase in the fraudulent tactic, AOL said.
However, there was much less spam related to pornography this year than in 2003, according to AOL.
AOL, which is the US's largest ISP, noted the "flavour" of spam changed noticeably in 2004 from last year, when the most widely sent junk e-mail subject lines included "Oprah", "Teens" and "Viagra".
Favourite 2004 spam terms were related to online pharmacy items such as Vioxx, phishing, dubious mortgage deals and stock offers as well as Viagra.
AOL, which bases its findings on spam reports sent by subscribers, said spammers this year became more sophisticated in their work.
"Gone are most small-time spammers, and what is left are the hardcore, kingpin spammers," the company claimed in a statement.