(YARA) YARA_PureCrypter
import "dotnet"
rule PureCrypter
{
meta:
author = "RussianPanda"
date = "2024-01-09"
reference = "https://www.zscaler.com/blogs/security-research/technical-analysis-purecrypter"
description = "Detects PureCrypter"
hash = "566d8749e166436792dfcbb5e5514f18c9afc0e1314833ac2e3d86f37ff2030f"
strings:
$s1 = {28 ?? 00 00 ?? 28 02 00 00 2B 28 ?? 00 00 (0A|06)}
$s2 = {73 ?? 00 00 0A}
$s3 = {73 ?? 00 00 06 6F ?? 00 00 06}
$s4 = {52 65 73 6F 75 72 63 65 4D 61 6E 61 67 65 72}
$s5 = {28 ?? 00 00 ?? 6F ?? 00 00 0A 28 03 00 00 2B ?? 6F ?? 00 00 0A 28 ?? 00 00 2B}
condition:
filesize < 6MB
and 4 of ($s*) and dotnet.number_of_resources > 0 and dotnet.number_of_resources < 2 and dotnet.resources[0].length > 300KB
}
import "dotnet"
rule PureCrypter_Core
{
meta:
author = "RussianPanda"
date = "2024-01-09"
reference = "https://www.zscaler.com/blogs/security-research/technical-analysis-purecrypter"
description = "Detects PureCrypter Core payload"
hash = "e4faa7d7a098414449abffb210fd874798207ee9d27643c8088676ff429b56b7"
strings:
$s1 = {47 5A 69 70 53 74 72 65 61 6D}
$s2 = {41 73 73 65 6D 62 6C 79 4C 6F 61 64 65 72 00 43 6F 73 74 75 72 61}
$s3 = {44 65 66 6C 61 74 65 53 74 72 65 61 6D}
$cnct = {72 ?? ?? 00 70 28 FB 00 00 0A 72 ?? ?? 00 70 28 ?? 00 00 0A}
$nr1 = {7B 00 31 00 31 00 31 00 31 00 31 00 2D 00 32 00 32 00 32 00 32 00 32 00 2D 00 34 00 30 00 30 00 30 00 31 00 2D 00 30 00 30 00 30 00 30 00 31 00 7D}
$nr2 = {7B 00 31 00 31 00 31 00 31 00 31 00 2D 00 32 00 32 00 32 00 32 00 32 00 2D 00 34 00 30 00 30 00 30 00 31 00 2D 00 30 00 30 00 30 00 30 00 32 00 7D}
$nr3 = {7B 00 31 00 31 00 31 00 31 00 31 00 2D 00 32 00 32 00 32 00 32 00 32 00 2D 00 32 00 30 00 30 00 30 00 31 00 2D 00 30 00 30 00 30 00 30 00 32 00 7D}
$nr4 = {7B 00 31 00 31 00 31 00 31 00 31 00 2D 00 32 00 32 00 32 00 32 00 32 00 2D 00 32 00 30 00 30 00 30 00 31 00 2D 00 30 00 30 00 30 00 30 00 31 00 7D}
condition:
filesize < 5MB and
all of ($s*)
and dotnet.number_of_resources > 4 and dotnet.number_of_resources < 6
and 2 of ($nr*) and dotnet.assembly_refs[1].name contains "protobuf-net"
and #cnct > 5
}
Associated Techniques
Technique Name | Technique ID's | Snippet(s) | OS |
---|---|---|---|
PureCrypter | U1433 |
Created
January 9, 2024
Last Revised
January 9, 2024