Supported formats

exav types each object by its content, never by its name, and runs the signatures scoped to that type. If the object is a container, it opens it and scans every member the same way, to any depth, under the limits. Anything it cannot fully examine is reported UNSCANNABLE, PASSWORD-PROTECTED or LIMITS-EXCEEDED, never OK (see Never a silent clean).

Containers are opened by the extractor, exav-unpack. Its Supported formats page has the codec-level detail; this page is what the scanner does with each kind of file.

File types

Every object, whatever its type, is matched against the body signatures with no target (Target:0), the file hash signatures (.hdb, .hsb) and the YARA rules. On top of that:

Type	What the scanner does with it	Signatures that apply to it alone
PE (Windows executables and DLLs)	Reads the entry point, sections, imports, icons, version information and Authenticode signer; unpacks a packed file (below)	Target:1; EP, section and VI offsets; section hashes (.mdb, .msb), import hashes (.imp), icons (.idb), signer block list (.crb); YARA pe and dotnet
ELF	Scanned as it is; a UPX-packed one is unpacked	Target:6; YARA elf. EP and section offsets do not resolve (gap)
Mach-O	A universal binary is split per architecture; each is scanned as it is, and a UPX-packed one unpacked	Target:9, with the same offset gap
OLE2 (legacy Office, MSI)	Every stream; VBA macros decompressed, Excel 4.0 (XLM) macros, Ole10Native payloads; encrypted Excel decrypted	Target:2
OOXML (.docx, .xlsx, .pptx)	Opened as the ZIP it is; told apart as Word, Excel or PowerPoint for Container:; encrypted documents decrypted	as for its members
PDF	Streams decoded through their filters (Flate, LZW, ASCII85, ASCIIHex, RunLength), JavaScript and URI and launch targets collected, the document decrypted. Image streams (DCT, JBIG2, JPX, CCITT) are matched as stored	Target:10
HTML	A normalised view (entities decoded, lowercased, whitespace collapsed) and, for script, a normalised and a deobfuscated JavaScript view; inline base64 assets extracted	Target:3, on the normalised view
RTF	Both an HTML and a text view; embedded objects extracted	Target:3 and Target:7
Email (MIME), MHTML	Every part decoded and scanned; a MIME document with no mail envelope is a saved web page (MHTML)	Target:4, on the raw message
Text, scripts	A normalised text view, and JavaScript views when the content looks like script; Script Encoder (#@~^) decoded; base64-encoded executables decoded (below)	Target:7, on the normalised view
Images	PNG, GIF, JPEG, TIFF, BMP; with the image-hash feature (on by default) also WebP, ICO, PNM, QOI, DDS, farbfeld, HDR, JPEG 2000 and JBIG2. Each is hashed as ClamAV’s sigtool --fuzzy-img hashes it	Target:5; fuzzy_img#
SWF	Compressed movies (CWS, ZWS) decompressed and rescanned	Target:11
Java class	The constant pool’s strings	Target:12

Target:8, 13 and 14 are not implemented; signatures scoped to them do not run. HandlerType: re-types an object and scans it again as the new type, as in ClamAV. Comparison with ClamAV covers the targets in detail.

Containers

Every format exav-unpack opens is opened when scanning, and its members scanned in turn:

• Archives: ZIP (every common method), 7z, RAR3 and RAR5, tar, CAB, CHM, ARJ, LHA, ZOO, ARC, ALZ, EGG, InstallShield .z, ar, cpio, xar.
• Compressed streams: gzip, bzip2, xz, zstd, lzip, LZ4, Unix compress (.Z), SZDD, KWAJ.
• Disk images: ISO 9660 and UDF, Apple DMG, the virtual disks VHD, VHDX, QCOW2 and VMDK reconstructed to the guest disk, GPT, APM and MBR partition maps, and the FAT, NTFS and ext2/3/4 filesystems inside them, WIM.
• Documents: OLE2, OOXML, PDF, RTF, HWP3, OneNote, Adobe XDP, Word and Excel 2003 flat XML.
• Mail: MIME, TNEF (winmail.dat), BinHex, uuencode.
• Installers and self-extractors: NSIS, SFX archives, AutoIt scripts (compiled ones too), Inno Setup recognised and reported.
• Other carriers: shortcuts (LNK), Python .pyc, AI model files (pickle opcodes, never executed, and safetensors headers), DXF and DWG drawings (their embedded objects and preview images; a drawing is not rendered).

A set split into byte-numbered parts (x.7z.001, x.7z.002, …) and met inside one container is joined and scanned whole. RAR and ZIP volume sets are not joined; a member continued in another volume is reported.

Found inside other files

Some payloads are not announced by the file that carries them. exav looks for them in every object:

• Executables and archives at an offset. A PE, ELF or Mach-O image, or a ZIP, gzip, bzip2, xz, 7z, RAR or CAB archive, found inside another file (appended to an image, embedded in a document) is carved and scanned in its own type: up to 16 images of each kind and 32 archives per object. An object holding more is reported LIMITS-EXCEEDED unless something is found, and the other members of its container are still scanned.
• Base64. A base64-encoded executable in a text file (a PE in a PowerShell one-liner) is decoded and scanned, and so are the data: URIs and base64 assets of HTML and flat-XML Office documents. --no-decode base64 turns it off (see Detection).

Packed executables

State	Packers
Unpacked, per format	UPX, every method, on PE, ELF and Mach-O; the aPLib family (Petite 2.x, FSG 2.0, NsPack); MPRESS, by running ClamAV’s own .cbc unpacker on exav’s bytecode interpreter, so only with bytecode.cvd loaded
Unpacked by running the stub	ASPack, MEW, Upack, WWPack, PESpin, Yoda’s Cryptor, and anything else that looks packed, under a bounded x86 interpreter that captures the image the stub rebuilds (PE stub emulation)
Reported UNSCANNABLE	A file whose packer exav identified but could not unpack. A file sent to the emulator only because of its shape is scanned as it is if nothing comes out
Reported, never unpacked	VMProtect, Themida/WinLicense, Enigma: virtualizers, where no original code exists in memory to recover

The unpacked image is scanned as a PE of its own, and what the bytecode signatures unpack is scanned too.

Size: what is read as it goes, and what is read whole

These are decoded as they are read, at any size: ZIP, tar, CAB, ISO/UDF, LHA, ar, cpio, TNEF, OneNote, SWF, SZDD, partition maps, self-extracting executables, universal Mach-O, .pyc, and the single-stream compressors. A member that decodes past --max-object-bytes goes to a spill file and is scanned from there, or is reported LIMITS-EXCEEDED with spilling off. The exceptions: ZIP Shrink, Reduce and Implode members, and encrypted ZIP members, are decoded whole under that limit.

A DMG is walked at any size, but each file in it is held whole, under --max-object-bytes; an encrypted DMG is decrypted whole under the same limit.

Every other container is read whole: one larger than --max-object-bytes (256 MiB by default) is reported LIMITS-EXCEEDED and its members are not scanned. That includes RAR, OLE, PDF, CHM, ARJ, xar, email, WIM, and the virtual disks and filesystems (VHD, VHDX, QCOW2, VMDK, FAT, NTFS, ext), which are often larger than that: raise --max-object-bytes where such images are expected. 7z is read whole too, but its members stream out of it.

A file of any size is scanned through a block cache rather than loaded. The checks that parse an object whole (a PE’s structure, YARA’s pe, elf and dotnet modules) apply up to --max-object-bytes; past it, an object one of them applied to is reported LIMITS-EXCEEDED unless something is found. See Limits and tuning.

Encryption and passwords

exav decrypts ZIP (ZipCrypto, WinZip AES), 7z, RAR3 and RAR5, PDF, encrypted DMG, legacy Excel and OOXML Office documents, and ARJ’s garbled and GOST-40 members. The schemes are listed with the extractor.

It tries, in order (a PDF’s empty user password goes first):

1. each --passwords (repeatable, or comma-separated in EXAV_PASSWORDS);
2. the lines of the --passwords-from file, kept verbatim, so a password may hold commas or spaces, and stays out of process listings;
3. the passwords of any ClamAV .pwdb database in the signature directory (cleartext or hex-encoded entries);
4. the built-in ones: infected, virus, malware, password and 123456 for ZIP and RAR (the malware-sharing convention), and VelvetSweatshop (Excel’s no-prompt default) and the empty password for Office.

Duplicates are dropped. Content still encrypted after that is reported PASSWORD-PROTECTED, never scanned as ciphertext and called clean. That covers a wrong or missing password, and the schemes exav detects but does not decrypt: RAR 2.0’s own cipher, PKWARE Strong Encryption, encrypted ALZ and EGG members, ARJ GOST-256, encrypted legacy Word .doc, and CryptFF.

Decryption needs the decrypt feature, on by default, and ARJ’s the arj feature (see Feature flags). Without them, that content is reported PASSWORD-PROTECTED.

What is reported instead of scanned

A container or codec exav recognises but does not decode is reported UNSCANNABLE rather than scanned as opaque bytes: ACE, StuffIt, Inno Setup, InstallShield MSI and InstallScript cabinets, AppleSingle and AppleDouble, lrzip, and a few codecs inside formats exav otherwise opens (ZIP methods 10, 94, 96 and 97, RAR 1.5 and 2.x compression, WIM LZMS, and others). The extractor’s complete gap list has every one and why it is open.

A format left out of a custom build is reported the same way.

Under --clamav-compat

--clamav-compat holds the scanner to what stock ClamAV opens, so a differential run compares like with like. It leaves these unopened, scanning the file as it is:

• ar and lzip archives, Inno Setup installers;
• the formats ClamAV has no type for: DMG, the virtual disks (VHD, VHDX, QCOW2, VMDK), Unix compress (.Z), DXF and DWG;
• UPX on ELF and Mach-O (UPX on PE stays on);
• base64 payloads;
• the image formats beyond PNG, GIF, JPEG, TIFF and BMP.

The PE unpackers stay on: compat narrows what is opened to compare with ClamAV, not the unpacking of executables.

Compared with ClamAV

The measurements below come from ClamAV 1.4.3 and 1.5.3. Where a container could hold the EICAR test file, it was scanned with it inside; otherwise its members were extracted with a third-party tool, hashed into a signature database, and the untouched container scanned.

Formats neither opens

Format / codec	ClamAV	exav
ACE	No support: 200 members of a real ACE went unextracted	UNSCANNABLE
StuffIt / StuffIt X	No support: real .sit and .sitx unextracted	UNSCANNABLE
Inno Setup	No support: stops at “Recognized MS-EXE/DLL”, 71 members unreached	UNSCANNABLE
ZIP method 10 (DCL Implode)	No support: enumerates the entry, then unsupported method (10)	UNSCANNABLE
ZIP methods 94 / 96 / 97 (MP3, JPEG, WavPack)	No support	UNSCANNABLE
PKWARE Strong Encryption	No support	PASSWORD-PROTECTED
WIM LZMS resources	No support for WIM at all: no CL_TYPE_WIM, all four test images clean	UNSCANNABLE; other WIM resources are decoded

None of these is a capability gap against ClamAV, but ClamAV answers OK for each, and exav says the members went unexamined. Not measured, and likely a gap: RAR 1.5 and 2.x compression, which ClamAV’s UnRAR-derived RAR support reads.

Checked against ClamAV’s own type list

These come from checking exav against ClamAV’s own CL_TYPE_* enumeration rather than a hand-assembled list. clamscan --debug reports dedicated submodules for EGG, ALZ and HWP, all on by default, and its shipped magic database types all five formats below.

Format	ClamAV	exav	Evidence of decoding in ClamAV
EGG (ESTsoft, Korean)	Decodes	Decodes (store/deflate/bzip2/LZMA/AZO)	EGG submodule on by default; Heuristics.Encrypted.EGG exists, so members are parsed deeply enough to detect encryption
ALZ (ESTsoft, Korean)	Decodes	Decodes (store/bzip2/deflate)	ALZ submodule on by default; magic added at flevel 210
HWP3 (Hangul Word Processor)	Decodes	Decodes (deflate body)	HWP submodule on by default, with its own scan-option bit, engine option MAX_RECHWP3 and --max-rechwp3 flag
ISHIELD_MSI (InstallShield MSI)	Types and handles	Recognised, reported UNSCANNABLE	dedicated CL_TYPE_ISHIELD_MSI
CRYPTFF	Types and handles	Recognised, reported PASSWORD-PROTECTED	dedicated CL_TYPE_CRYPTFF

EGG and ALZ matter for Korean-language targets, where ALZip is common; HWP3 is the Korean government’s standard document format and a recurring spear-phishing carrier.

Formats ClamAV does not recognise

A format with no detection is the weaker failure: the file is scanned as whatever it types as, its members are never reached, and the scan can come back clean.

Format	ClamAV	exav
InstallShield .z archive	No support	Decoded
ext2/3/4	No support	Decoded
ZOO	No support	Decoded
VHD, VHDX, QCOW2, VMDK, NTFS, FAT	No support	Decoded
InstallShield InstallScript cabinet	No support	Recognised, reported UNSCANNABLE
AppleSingle / AppleDouble	No support	Recognised, reported UNSCANNABLE
lrzip	No support	Recognised, reported UNSCANNABLE

Evidence for what ClamAV does not open has the disk image measurements.

Packers

ClamAV natively unpacks 10 packer families, each with a hand-written submodule. exav unpacks four of them with dedicated decoders and the rest through the emulator. SUE and Yoda’s Protector (not Yoda’s Cryptor) are detection-only in ClamAV, covered by PUA packer signatures in the optional .?du databases, and so is MPRESS outside its bytecode signature.