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Obfuscated Files or Information: Software Packing

Description from ATT&CK

Adversaries may perform software packing or virtual machine software protection to conceal their code. Software packing is a method of compressing or encrypting an executable. Packing an executable changes the file signature in an attempt to avoid signature-based detection. Most decompression techniques decompress the executable code in memory. Virtual machine software protection translates an executable's original code into a special format that only a special virtual machine can run. A virtual machine is then called to run this code.(Citation: ESET FinFisher Jan 2018)

Utilities used to perform software packing are called packers. Example packers are MPRESS and UPX. A more comprehensive list of known packers is available, but adversaries may create their own packing techniques that do not leave the same artifacts as well-known packers to evade defenses.(Citation: Awesome Executable Packing)

Atomic Tests

Atomic Test #1 - Binary simply packed by UPX (linux)

Copies and then runs a simple binary (just outputting "the cake is a lie"), that was packed by UPX. No other protection/compression were applied.

Supported Platforms: linux

auto_generated_guid: 11c46cd8-e471-450e-acb8-52a1216ae6a4

Inputs:

Name Description Type Default Value
bin_path Packed binary Path PathToAtomicsFolder/T1027.002/bin/linux/test_upx

Attack Commands: Run with sh!

1
2
cp #{bin_path} /tmp/packed_bin && /tmp/packed_bin

Cleanup Commands:

1
2
rm /tmp/packed_bin

Atomic Test #2 - Binary packed by UPX, with modified headers (linux)

Copies and then runs a simple binary (just outputting "the cake is a lie"), that was packed by UPX.

The UPX magic number (

1
0x55505821
, "
1
UPX!
") was changed to (
1
0x4c4f5452
, "
1
LOTR
"). This prevents the binary from being detected by some methods, and especially UPX is not able to uncompress it any more.

Supported Platforms: linux

auto_generated_guid: f06197f8-ff46-48c2-a0c6-afc1b50665e1

Inputs:

Name Description Type Default Value
bin_path Packed binary Path PathToAtomicsFolder/T1027.002/bin/linux/test_upx_header_changed

Attack Commands: Run with sh!

1
2
cp #{bin_path} /tmp/packed_bin && /tmp/packed_bin

Cleanup Commands:

1
2
rm /tmp/packed_bin

Atomic Test #3 - Binary simply packed by UPX

Copies and then runs a simple binary (just outputting "the cake is a lie"), that was packed by UPX. No other protection/compression were applied.

Supported Platforms: macos

auto_generated_guid: b16ef901-00bb-4dda-b4fc-a04db5067e20

Inputs:

Name Description Type Default Value
bin_path Packed binary Path PathToAtomicsFolder/T1027.002/bin/darwin/test_upx

Attack Commands: Run with sh!

1
2
cp #{bin_path} /tmp/packed_bin && /tmp/packed_bin

Cleanup Commands:

1
2
rm /tmp/packed_bin

Atomic Test #4 - Binary packed by UPX, with modified headers

Copies and then runs a simple binary (just outputting "the cake is a lie"), that was packed by UPX.

The UPX magic number (

1
0x55505821
, "
1
UPX!
") was changed to (
1
0x4c4f5452
, "
1
LOTR
"). This prevents the binary from being detected by some methods, and especially UPX is not able to uncompress it any more.

Supported Platforms: macos

auto_generated_guid: 4d46e16b-5765-4046-9f25-a600d3e65e4d

Inputs:

Name Description Type Default Value
bin_path Packed binary Path PathToAtomicsFolder/T1027.002/bin/darwin/test_upx_header_changed

Attack Commands: Run with sh!

1
2
cp #{bin_path} /tmp/packed_bin && /tmp/packed_bin

Cleanup Commands:

1
2
rm /tmp/packed_bin

source