BUSINESS BRIEFING / INTERNET

For the third time this year, Twitter Inc. was the victim of a security breach stemming from a simple end run around its defenses: A hacker guessed the password for an employee’s personal e-mail account and worked from there to steal confidential company documents.

The incident highlights the dangers of a trend toward storing data online, a practice known as cloud computing.

The hacker claims to have employee salaries and credit card numbers, job applicants’ resumes, internal meeting reports and growth projections.