Click the group name, then use the orange bars to indicate the. Locate and select the executable file of the application you want to add. Click New application rule and select a group (vendor). Click Application settings at the bottom of the screen. Sejtko said that AVAST researchers would discuss the use of filters to hide exploits at the forthcoming Caro 2011 Workshop held in Prague on May 5-6. To add an application to an existing group: Open Avast Antivirus and go to Protection Firewall. Techniques that mask exploits in this way will remain relatively demanding for antivirus scanners to pick up because they require the ruse to be unpicked using a dedicated algorithm rather than a simple signature. Avast had now updated its software to detect the JBIG2Decode attack.

That is probably why no one else is able to detect it,” said Sejtko. “We have seen this nasty trick being used in a targeted attack and have seen it used so far in a relatively small number of general attacks. In addition, AVAST researchers believe the same JBIG2Decode filter technique is being used to hide other exploits, including, a TrueType font exploit from September 2010 affecting Reader 9.3.4 running on all platforms. Current versions, Reader X 10.x, are not affected although many users will still be using older versions. The TIFF vulnerability being targeted is CVE-2010-0188 from February 2010, which affects Adobe Reader 9.3 or earlier versions running on Windows, Mac and Unix. Part of the problem was the scope offered by the PDF specification to use filters such as JBIG2Decode in unusual ways, and even to use several of them at once in a layered fashion, he said. “And that’s the reason why our scanner wasn’t successful in decoding the original content - we hadn’t expected such behavior.” Click the Firefox menu again, and then click Exit.

Right-click on the printprinter setting and select Reset. “Who would have thought that a pure image algorithm might be used as a standard filter on any object stream you want?” said AVAST virus analyst, Jiri Sejtko, in a blog. Type the configuration settings page by typing about:config in the address bar of the Mozilla Firefox browser. īecause the content appears to antivirus software as a harmless two-dimensional TIFF image, the malicious exploit goes unnoticed. The trick involves hiding a common Adobe Reader exploit inside a PDF (Portable Document Format) file by encoding it with the JBIG2Decode filter, normally used to minimize file sizes when embedding monochrome TIFF (Tagged Image File Format) images inside PDFs. Criminals have started using an obscure image filter to make malicious PDF files all but invisible to many antivirus programs, Czech security firm AVAST Software said.

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