Re: corrupted files reported by sophie & SAVI
Markus Stumpf <[email protected]>
| Newsgroups | gmane.comp.security.virus.vtools |
|---|---|
| Organization | SpaceNet AG, Muenchen, Germany |
| Message-ID | <[email protected]> |
On Sat, Jan 24, 2004 at 10:20:50AM +0100, Maciej Uhlig wrote:
> what heuristic does Sophos apply to find 11-byte ASCII text file needs
> decoding and
> report it as 'corrupted'???
A different ;-)
But "file" also reports false guesses often enough.
> these files are reported by sweep as virus free. you see, sweep is a black
> box.
> it gets from SAVI: 'file corrupted' but it puts to the user 'no viruses were
> discovered', I suppose.
> which is true.... but sophie is more precise...
No, sweep also reports "file corrupted" if it thinks the file is
corrupted. It probably only uses a different set of options.
> > With the fix to correctly set the type for the Grp* options
> > and with setting "ZipUseChd: 1" and "limit_classif: 5000", nearly
> > all my problems with warning about corrupt files went away.
>
> so I second a request from Ed: please let us see your /etc/sophie.savi.
I have atteched it to this mail.
> are you sure the file is being unpacked/decoded at all when ZipUseChd option
> is set :-)?
> maybe it is skipped? we don't know what this undocumented option does in
> fact. we only
> know it supressess the number of reports about corrupted files.
I had different ZIP files. Some of the were fine some reported
"corrupt file". Even the latter where decodable perfectly by unzip.
Repacking the contents revealed a slightly different ZIP that could be
scanned without problems. Maybe different decoders produce different
ZIP compressed files. zipinfo reports for the "corrupt file":
-rw---- 2.0 fat 135858 bl defN 22-Jan-04 17:10 BF001326.dbf
1 file, 135858 bytes uncompressed, 9379 bytes compressed: 93.1%
The "bl" flags mean
b = binary
l = there is an extended local header but no extra field
Maybe - *speculating* - Chd means something like "check header" and
without that flag the scanner reports type "l" ZIP archives as being
corrupt.
I have no idea what that type "l" really means.
\Maex
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sophie.savi
(text/plain, 9.7 KB)
############################################################################# # # # Meaningful descriptions were taken from SAVI Developer Toolkit Supplement # # document. # # # # Meaningless descriptions were, of course, added by me :) # # # ############################################################################# ############################################################################# # # # Group options automatically activate/deactivate all options that belong # # to the group. You'll have to figure out what belongs where, sorry :) # # # # If you want to deactivate certain feature from a group, just set it to 0 # # but make sure group definitions do remain at the top of this file # ############################################################################# # Executable files GrpExecutable: 1 # All archive and compressed archive file formats (e.g. ZIP, UUE, etc) GrpArchiveUnpack: 1 # File formats that contain an executable stub that automatically decompresses # the body of the file GrpSelfExtract: 1 # File formats commonly in use on the internet GrpInternet: 1 # Microsoft Office file formats GrpMSOffice: 1 # File formats that do not fall into any of the above categories GrpMisc: 1 # Any option that is part of a group is also included in this group # (NOTE: I have no idea what this really means :) GrpSuper: 0 # Enables or disables disinfection of all files for which disinfection is # supported GrpDisinfect: 0 ######################### # # # Configuration options # # # ######################### # Controls handling of Macintosh resounce and data fork files (on platforms # where these are supported). Settings are: # # 0 = Disabled # 1 = SOPHOS_DOS_FILES (enable scanning for Mac viruses) # 2 = SOPHOS_MAC_FILES (scan data fork files for DOS viruses) # 3 = SOPHOS_DOS_AND_MAC_FILES (mix :) #NamespaceSupport: 0 # Enables full sweeping, which performs extensive fixed pattern matching as # well as the standard intelligent virus search. Turning on this option # might have severe performance implications. FullSweep: 1 Base64: 1 # Controls the ability to scan inside supported types of dynamically # compressed executables. DynamicDecompression: 1 # Enables a fallback mechanism that has been deployed in the past when new # file structures are encountered. Sophos recommends that you keep this # option turned off. #FullMacroSweep: 0 # Enables the intelligent scanning of OLE2 (Microsoft Office) format # documents. Sophos recommends that this option should be turned on. OLE2Handling: 1 # Microsoft Office documents that contain executable macros will usually have # a single bit in the file header set to 1 to indicate the presence of # executable code. Under normal circumstances macros contained in a file that # does not have this bit set are not able to execute. If this option is # turned off, the Virus Engine will scan only files with this template bit # set to 1. Sophos recommends that you keep this option turned on. IgnoreTemplateBit: 1 # This option enables the scanning of Microsoft Visual Basic for Applications # embedded in supported file types, like Office and Visio documents. VBA3Handling: 1 # This option enables the scanning of Microsoft Visual Basic for Applications # embedded in supported file types, like Office and Visio documents. VBA5Handling: 1 # Password-protected Office 95 documents are encrypted with a very simple # algorithm. Enabling this option causes the virus engine to break this # encryption to search for viruses. OF95DecryptHandling: 1 # Enables checking for files embedded in Mirosoft Help files. HelpHandling: 1 # Decompresses the text part of a VBA5 project before scanning. This area is # often corrupted, but can help positive identification of some viruses. DecompressVBA5: 1 # Enables the 16-bit x86 emulation engine, which assists in the detection of # polymorphic executable file viruses. Sophos recommends this option should be # turned on. Emulation: 1 # Enables the intelligent scanning of Win32/PE format files. This is the # standard format for Windows executable binaries such as .exe and .dll. PEHandling: 1 # Enables scanning of Excel formulas for known formula viruses. Formulas # occupy cells on the worksheet and should not be confused with macros. ExcelFormulaHandling: 1 # Enables the scanning of macros in PowerPoint presentations. PowerPointMacroHandling: 1 # Enables the scanning of files embedded within PowerPoint presentations. PowerPointEmbeddedHandling: 1 # Enables the scanning of VBA macros in Microsoft Project. ProjectHandling: 1 # Enables scanning inside ZIP archives. ZipDecompression: 1 ZipUseChd: 1 # Enables decompression of Arj archives. ArjDecompression: 1 # Enables decompression of RAR archives. RarDecompression: 1 # Enables the virus engine to decode EEUncoded files. The UUEncode portion # must start within the first 4k of the document. UueDecompression: 1 # Enables decompression of Gzipped archives. GZipDecompression: 1 # Enables scanning inside UNIX tar archives. TarDecompression: 1 # Enables decompression of Cmz archives. CmzDecompression: 1 # Contols the ability to extract files from BinHex archives. HqxDecompression: 1 # Controls the ability to look inside MacBinary archives. MbinDecompression: 1 # Controls SAVI's ability to scan inside certain types of container file. # Sophos recommends that this options should be turned on. LoopBackEnabled: 1 # Contols the maximum number of times the engine will recurse into archives # when they are found (e.g. when a zip file is compressed within another zip # file). The maximum value is 100, but SAVI internally has some extra levels # of recursion to cover internal data streams found within some file types. MaxRecursionDepth: 16 # Enables decompression of Lha archives. Lha: 1 # Enables the virus engine to search in supported types of self-extracting # archive. SfxArchives: 1 # Enables decoding of files encoded with the Microsoft TNEF format, used by # some mail client applications. TnefAttachmentHandling: 1 # Controls the ability to scan inside files compressed with the Microsoft # compression utility. MSCompress: 1 # Enables decompression of Microsoft Cabinet files (.cab) (Partial files at # the beginning and end of multi-part cabinet files will not be fully # scanned #MSCabinet: 1 # Applies to Microsoft Office and other OLE2 format files. When this option is # enabled, calls to DisinfectFile() all macros present in the document are # deleted, regardless of whether or not they are viral. #DeleteAllMacros: 0 # Enables the scanning of encoded VBScript files. Vbe: 1 # Some executable file viruses can be removed from files fairly safely. This # option enables that process. Sophos recommends that infected executables are # replaced from the original installation disks as soon as possible. #ExecFileDisinfection: 0 # Enables the scanning of Microsoft Visio files. VisioFileHandling: 1 # Enables decoding and scanning inside a MIME encoded message block. Mime: 0 # Enables the detection of macro viruses within Microsoft Office documents # saved in ActiveMime document format. ActiveMimeHandling: 1 # Causes the entire project containing any viral macros to be removed during # disinfection. #DelVBA5Project: 0 # Enables the handling of scrap objects that are used in the transfer of data # between certain applications. ScrapObjectHandling: 1 # Deals with another type of data within Office documents. SrpStreamHandling: 1 # Controls the ability of the engine to understand Microsoft Office 2001 # files (Macintosh only) Office2001Handling: 1 # Enables scanning inside UPX-compressed self-extracting executable archives. Upx: 1 # FIXME: No idea what this is used for #Mac: 0 # FIXME: No idea what this is used for #SafeMacDfHandling: 0 # Enables the scanning of Palm Pilot format files (.prc). PalmPilotHandling: 1 # Controls the PDF file interpretation module. Pdf: 1 # Enables scanning for objects that may be embedded inside Rich Text FOrmat # files. Rtf: 1 # Controls the module that optimises scanning in HTML files. Html: 1 # Controls the module that interprets ELF binary files. This format is used # for many Linux and FreeBSD executable files. Elf: 1 # Enables the scanning of WordBasic. WordB: 1 # Enables scanning of files contained within Outlook Express mailboxes. OutlookExpress: 1 # FIXME: Well, I have some idea... Java: 1 # FIXME: Well, I have some idea... Access: 1 # FIXME: No idea what this is used for #AppleSingle: 0 # FIXME: No idea what this is used for VbFiltering: 1 ####################################################### # # # DO NO SET/USE ANY OF THESE CONFIGURATION OPTIONS!!! # # # ####################################################### # The passed string defines the full path name of the directory in which the # main virus data file is located. The name should not have a trailing # directory separator character. #VirusDataDir: # The passed string defines the name of the virus data file. This name should # not include a directory component (this is defined by the VirusDataDir # setting) or a file extension. For example, if the main virus data file name # is vdl.dat then this string should be passed as vdl. #VirusDataName: # The passed string defines the full path name of the directory in which SAVI # should search for IDE files. IdeDir: