Arkin also credited Nicolas Sylvain, a software engineer at Google, and that company's Chrome browser team, with helping Adobe craft Reader's Protected Mode.

Adobe's effort, which began more than a year ago, has been focused on what Arkin called the "broker process," which decides what functions Reader can conduct outside the sandbox, such as writing to disk or launching an attachment or executable from within the software. The broker is limited by preset policies, which users can modify, that restrict those kinds of functions, said Arkin.

Although he refused to guarantee that the broker process itself wouldn't be exploitable, Arkin said he was confident that it would be "rock solid" when Reader 10 shipped, in part because the code for the broker is all new and was written with security in mind.

Last year, Adobe adopted a new development practice called Secure Product Lifecycle (SPLC), an approach similar to Microsoft's much better known Software Development Lifecycle (SDL). Both involve several security-specific steps that programmers go through to make their software less likely to harbour bugs.

That move and others, including a quarterly security patch schedule, were made in 2009 in reaction to criticism following the company's slow fix for a flaw that was being exploited by attackers earlier that year.

Protected Mode is another aspect of that campaign, said Arkin, adding, "This is a really big change for Reader."

Reader and the associated Acrobat PDF creation program have been bombarded with attacks for the past 18 months, while Reader and Acrobat vulnerability tallies have also climbed dramatically.

Antivirus vendors McAfee and Symantec, for example, have reported surges in attacks exploiting bugs in Reader. Last April, McAfee said that exploits of Reader jumped 65% in the first quarter of 2010 compared with all of 2009. Last week, Danish bug-tracking firm Secunia chimed in, saying that the bulk of a ballooning number of bugs facing Windows users this year could be traced to third-party software like Adobe's.