# [HIGH] Log4Shell in a nutshell (for non-developers & non-Java developers)

**Source:** Snyk
**Published:** 2021-12-15
**Article:** https://snyk.io/blog/log4shell-in-a-nutshell/

## Threat Profile

Snyk Blog In this article
Written by Micah Silverman 
December 15, 2021
0 mins read Editor's note (28 Dec 2021 at 7:35 p.m. GMT): The Log4j team released a new security update that found 2.17.0 to be vulnerable to remote code execution, identified by CVE-2021-44832. We recommend upgrading to the latest version, which at this time is 2.17.1. 
Editor's note (18 Dec 2021 at 6:55 p.m. GMT): The Log4j situation is rapidly changing and we are updating our blogs as new information becomes available. It…

## Indicators of Compromise (high-fidelity only)

- **CVE:** `CVE-2021-44832`
- **CVE:** `CVE-2021-44228`
- **CVE:** `CVE-2021-45046`
- **CVE:** `CVE-2021-45105`

## MITRE ATT&CK Techniques

- **T1190** — Exploit Public-Facing Application
- **T1195.002** — Compromise Software Supply Chain
- **T1204.002** — User Execution: Malicious File

## Kill chain phases observed

_(none detected from narrative keywords)_

## Recommended hunts

### Trusted vendor binary / installer launching unusual children

`UC_SUPPLY_CHAIN` · phase: **exploit** · confidence: **Medium**

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime
    from datamodel=Endpoint.Processes
    where Processes.parent_process_name IN ("setup.exe","installer.exe","update.exe")
      AND Processes.process_name IN ("powershell.exe","cmd.exe","rundll32.exe","regsvr32.exe","mshta.exe","wscript.exe","cscript.exe","wmic.exe","bitsadmin.exe")
    by Processes.dest, Processes.user, Processes.parent_process_name, Processes.process_name, Processes.process
| `drop_dm_object_name(Processes)`
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where AccountName !endswith "$"
| where InitiatingProcessFileName in~ ("setup.exe","installer.exe","update.exe")
| where FileName in~ ("powershell.exe","cmd.exe","rundll32.exe","regsvr32.exe","mshta.exe","wscript.exe","cscript.exe","wmic.exe","bitsadmin.exe")
| project Timestamp, DeviceName, AccountName, InitiatingProcessFileName, FileName, ProcessCommandLine
```

### Article-specific behavioural hunt — Log4Shell in a nutshell (for non-developers & non-Java developers)

`UC_2512_2` · phase: **install** · confidence: **High**

**Splunk SPL (CIM):**
```spl
``` Article-specific bespoke detection — Log4Shell in a nutshell (for non-developers & non-Java developers) ```
| tstats `summariesonly` count
    from datamodel=Endpoint.Filesystem
    where Filesystem.action IN ("created","modified")
      AND (Filesystem.file_path="*/tmp/pwned*")
    by Filesystem.dest, Filesystem.user, Filesystem.process_name,
       Filesystem.file_path, Filesystem.file_name
| `drop_dm_object_name(Filesystem)`
```

**Defender KQL:**
```kql
// Article-specific bespoke detection — Log4Shell in a nutshell (for non-developers & non-Java developers)
// Hunts the actual binaries / paths / commandline fragments named
// in the article instead of a generic technique-class template.

// File-creation events for the named binaries / paths
DeviceFileEvents
| where Timestamp > ago(30d)
| where ActionType in ("FileCreated","FileModified")
| where (FolderPath has_any ("/tmp/pwned"))
| project Timestamp, DeviceName, AccountName, FolderPath,
          FileName, ActionType, InitiatingProcessFileName,
          InitiatingProcessCommandLine
| order by Timestamp desc
```

### IOC-driven hunts (use shared templates)

These are standard IOC-substitution hunts — the canonical SPL and KQL live once in [`_TEMPLATES.md`](../_TEMPLATES.md), so we don't repeat the same boilerplate on every CVE / hash / network-IOC briefing.

- **Asset exposure — vulnerability matches article CVE(s)** ([template](../_TEMPLATES.md#asset-exposure)) — phase: **recon**, confidence: **High**
  - CVE(s): `CVE-2021-44832`, `CVE-2021-44228`, `CVE-2021-45046`, `CVE-2021-45105`


## Why this matters

Severity classified as **HIGH** based on: CVE present, 3 use case(s) fired, 3 technique(s) inferred. Read the full article for actor attribution, tooling details, and any defanged IOCs in the body that aren't visible in the RSS summary.