Securing The PDF

The PDF file is getting some major security attention these days: first, Adobe's long-awaited sandboxing feature that rolled out with the new Reader X late last week, and now a tool from a start-up that opens PDFs in a separate virtualized environment.

Poisoned PDFs are one of the most popular vehicles for carrying malicious code, and after beefing up the patching cycle for the heavily targeted application during the past year, Adobe added Protected Mode for the files, which basically places them in a sandbox that separates them from the operating system and other apps so if they are infected, they can't hurt other aspects of the machine.

Invincea's new Document Protection moves Adobe Reader into a virtual environment so that the document can be opened in a quarantined area that also detects, cleans up, and logs forensics information about the malware. The software is offered as a plug-in to Invincea's virtual browser environment, which provides a separate space for browsing so that Web-borne malware threats are kept separate from the system itself.

Anup Ghosh, founder of Invincea, says his firm's tool can be used as another layer of PDF protection along with Reader X's sandbox. Adobe's Protected Mode sandbox helps protect against exploits against Reader that occur in the rendering engine of the app, where most of today's exploits occur, Ghosh says. "JavaScripts run and happen there. [But] a number of components not within that rendering engine are not covered by the [Adobe] sandbox," he says. "In reality, there's a lot of code in Adobe that's outside the rendering engine" and ripe for targeting, he says.

A recent zero-day exploit released earlier this month against Reader was an exploit that targeted a plug-in to the app, he says. "It was not in the rendering engine, so it appears to me that Reader X would not have protected against that type of exploit," Invincea's Ghosh says. Protected Mode can't stop an attacker from using Reader to attack other parts of the host, or other machines on the network, for instance, according to Invincea.

Even so, security experts say Adobe's Protected Mode is a significant step by Adobe in locking down the beleaguered PDF.

Brad Arkin, senior director of product security and privacy, says sandboxing handles most of the real-world attacks against PDFs. "Real-world attacks today are almost always some variant of a memory trespass vulnerability," Arkin said in an interview in July, when Adobe first announced sandboxing. Sandboxing, which restricts what an attacker is able to do with a PDF file, should eliminate many of those types of threats, he says.

The first release of Protected Mode keeps all "write" calls inside the sandbox so if a PDF is infected, the malicious code can't spread outside the file to the system or other files. An upcoming version of the feature will prevent attackers from reading information on the victim's machine.

Richard Stiennon, chief research analyst at IT-Harvest, says Invincea's tool is handy for enterprises in that it issues reporting on malware or attempted attacks that can be used for forensics, for example. "It gives you stats on what the PDF is doing, what the command and control [server] is doing, and what exploit is attempting to [load]," Stiennon says. The tool would be overkill for consumers, but that's where Adobe's Protected Mode could come in, he says.

Meanwhile, the Invincea PDF protection plug-in works as the PDF handler for the system, Ghosh notes. "Whenever you open a PDF -- in an email, on your desktop, or in Flash -- we will open that doc in Document Protection for Adobe Reader," he says. "We take over for Adobe. We literally copy the file from wherever you open it into our virtual file system, where it opens it in Adobe there."

The software, which could eventually be sold as a stand-alone package, is bundled with Invincea Browser Protection, and is priced at an extra $15 per desktop, for about $75 per desktop per year (not including volume discounts). So far, the Defense Department and other national security organizations have been the main customers for Invincea with its browser product, but financial services and healthcare also are on the list, according to Invincea. Invincea was originally funded by the Defense Advanced Research Projects Agency (DARPA) to build a prototype virtualized browser, which ultimately led to its Invincea Browser Protection and, now, Document Protection.

Of course, no security control is foolproof. Researchers have been hammering away at virtual environments and are expected to eventually take a shot at Adobe's sandbox, looking for holes.

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