Adobe Systems Inc., the biggest maker of graphic-design software, said hackers broke into its networks and stole personal data on 2.9 million customers and source code for popular products including Acrobat and ColdFusion.

The customer information includes names and encrypted credit- and debit-card numbers, and Adobe is notifying victims and resetting the passwords for affected accounts on its website, Brad Arkin, chief security officer, wrote yesterday in a blog post. The San Jose, California-based company doesn't believe the hackers got access to decrypted card numbers, Arkin wrote.

While there are established procedures for consumers to fight financial fraud after a data breach -- primarily contacting banks and placing fraud alerts on credit reports -- the theft of source code presents a more vexing challenge for technology companies. In a separate blog post, Arkin wrote that Adobe believes the same hackers may have stolen code for Adobe Acrobat, ColdFusion, ColdFusion Builder and other products.

Such thefts potentially open the door for hacking attacks on Adobe customers, as source code can allow hackers to identify previously unknown weaknesses in the software and deliver specially crafted attacks. Adobe isn't aware of any "zero-day" attacks targeting its products based on the theft, Arkin wrote. The term refers to attacks that begin before companies know the vulnerabilities in their products exist.

Adobe didn't specify whether the code was for the latest versions of the software, which would amplify the threat of hacking attacks.

Symantec Corp., the biggest maker of computer-security software, said in February 2012 that it was the target of an attempt to extort $50,000 from the company to keep stolen source code for its products off the Internet. Symantec said the code was stolen in a 2006 incursion into its networks and mostly applied to obsolete products, which muted reaction to the incident.

Adobe shares slipped 0.5 percent to $50.61 yesterday in late trading after falling 1.2 percent to $50.88 at the New York close. They have gained 35 percent this year.