Far too many web users rely on the same login details for multiple websites, says Trusteer.
Using statistics gathered over the past year from the bank login protection software that runs on 4 million PCs, the security vendor found that 73 percent of users were using the password for their online bank sites to access at least one other website.
Furthermore, 65 percent compounded this risky behaviour by using the same ID, while nearly half were lax enough to re-use both.
The problem with this behaviour is that if it was ever an acceptable way to access websites, this week's Twitter phishing hack shows that password and user name re-use is now asking for trouble.
This week, Twitter alerted users to an attack on the social networking site's accounts that involved logins harvested from a network of scam Torrent file-sharing sites that had been active for years.
Employing lateral thinking, the criminals worked out well in advance that users of the site would probably re-use those same logins enough times to make an attack on a higher-profile site viable at a later date.
"The takeaway from this is that people are continuing to use the same email address and password (or a variant) on multiple sites," Twitter said in a blog.
"Through our discussions with affected users, we've discovered a high correlation between folks who have used third party forums and download sites and folks who were on our list of possibly affected accounts."
In Trusteer's view - it has a password enforcement system to sell - passwords are inherently limited. People cannot create and remember multiple passwords and logins, leading to their inevitable re-use for the sake of convenience.
"Our findings [...] reveal that consumers are not aware, or are choosing to ignore, the security implications of reusing their banking credentials on multiple websites," said Trusteer's CTO, Amit Klein.
The company's practical advice for users who don't wish to use a dedicated password application or password management website was to create three separate logins, one for financial sites, a second for any site holding sensitive data, and a third for sites not holding anything of value.
See also: Twitter hits 75 million user mark