The techniques used by the attackers highlight the dangers of a broader trend promoted by Google Inc. and others toward storing more data online, instead of on computers under your control.

The shift toward doing more over the Web — a practice known as "cloud computing" — means that mistakes employees make in their private lives can do serious damage to their employers, because a single e-mail account can tie the two worlds together.

Stealing the password for someone's Gmail account, for example, not only gives the hacker access to that person's personal e-mail, but also to any other Google applications they might use for work, like those used to create spreadsheets or presentations.

That's apparently what happened to Twitter, which shares confidential data within the company through the Google Apps package that incorporates e-mail, word processing, spreadsheet, calendar and other Google services for $50 per user per year.