.Net Reactor

.NET Reactor is used to prevent reverse engineering by adding different protection layers to .NET assemblies. Beside standard obfuscation techniques it includes special features like NecroBit, Virtualization, x86 Code Generation or Anti Tampering.

Technique Identifier

U1423

Evasion Categories

Packers

Detection Rules

rule SUSP_OBF_NET_Reactor_Native_Stub_Jan24 {
	meta:
		description = "Detects native packer stub for version 4.5-4.7 of .NET Reactor. A pirated copy of version 4.5 of this commercial obfuscation solution is used by various malware families like BlackBit, RedLine, AgentTesla etc."
		author = "Jonathan Peters"
		date = "2024-01-05"
		reference = "https://notes.netbytesec.com/2023/08/understand-ransomware-ttps-blackbit.html"
		hash = "6e8a7adf680bede7b8429a18815c232004057607fdfbf0f4b0fb1deba71c5df7"
		score = 70
	strings:
		$op = {C6 44 24 18 E0 C6 44 24 19 3B C6 44 24 1A 8D C6 44 24 1B 2A C6 44 24 1C A2 C6 44 24 1D 2A C6 44 24 1E 2A C6 44 24 1F 41 C6 44 24 20 D3 C6 44 24 21 20 C6 44 24 22 64 C6 44 24 23 06 C6 44 24 24 8A C6 44 24 25 F7 C6 44 24 26 3D C6 44 24 27 9D C6 44 24 28 D9 C6 44 24 29 EE C6 44 24 2A 15 C6 44 24 2B 68 C6 44 24 2C F4 C6 44 24 2D 76 C6 44 24 2E B9 C6 44 24 2F 34 C6 44 24 30 BF C6 44 24 31 1E C6 44 24 32 E7 C6 44 24 33 78 C6 44 24 34 98 C6 44 24 35 E9 C6 44 24 36 6F C6 44 24 37 B4}
	condition:
		for any i in (0..pe.number_of_resources-1) : (pe.resources[i].name_string == "_\x00_\x00")
		and $op
}

rule SUSP_OBF_NET_Reactor_Indicators_Jan24
{
	meta:
		description = "Detects indicators of .NET Reactors managed obfuscation. Reactor is a commercial obfuscation solution, pirated versions are often abused by threat actors."
		author = "Jonathan Peters"
		date = "2024-01-09"
		reference = "https://www.eziriz.com/dotnet_reactor.htm"
		hash = "be842a9de19cfbf42ea5a94e3143d58390a1abd1e72ebfec5deeb8107dddf038"
		score = 65
	strings:
		$ = { 33 7B 00 [9] 00 2D 00 [9] 00 2D 00 [9] 00 2D 00 [9] 00 7D 00 }
		$ = { 3C 50 72 69 76 61 74 65 49 6D 70 6C 65 6D 65 6E 74 61 74 69 6F 6E 44 65 74 61 69 6C 73 3E 7B [8] 2D [4] 2D [4] 2D [4] 2D [12] 7D }
		$ = { 3C 4D 6F 64 75 6C 65 3E 7B [8] 2D [4] 2D [4] 2D [4] 2D [12] 7D }
	condition:
      uint16(0) == 0x5a4d
		and 2 of them
}

Contributor

Jonathan Peters

Additional Resources

External Links

The resources provided below are associated links that will give you even more detailed information and research on current evasion technique. It is important to note that, while these resources may be helpful, it is important to exercise caution when following external links. As always, be careful when clicking on links from unknown sources, as they may lead to malicious content.

.NET Reactor - .NET Protection, .NET Obfuscator and Licensing

Matching Samples 10 most recent

Sample Name	Matching Techniques	First Seen	Last Seen
library.dll	8	2026-03-06	4 weeks, 1 day ago
DelphinDesktop.dll	8	2026-03-05	4 weeks, 2 days ago
DTC22.dll	4	2026-02-11	1 month, 3 weeks ago
UMLoader.dll	7	2026-01-27	2 months, 1 week ago
DelphinDesktop.dll	9	2025-08-31	7 months ago
Xtra_Slayed-cleaned-cleaned.exe	5	2025-04-29	11 months ago
AdvancedSystemProtector.exe	5	2025-02-12	1 year, 1 month ago
NFA Login Tool.exe	8	2025-02-05	1 year, 1 month ago

View All

Created

June 20, 2022

Last Revised

March 24, 2026