# [HIGH] What is a backdoor? Let’s build one with Node.js

**Source:** Snyk
**Published:** 2020-03-19
**Article:** https://snyk.io/blog/what-is-a-backdoor/

## Threat Profile

Snyk Blog In this article
Written by Ulises Gascón 
March 19, 2020
0 mins read A backdoor in our code that can perform OS injection is one of the most scary scenarios ever. Currently, npm has more than 1.2M of public packages available. For the last three years, our dependencies have become the perfect target for cybercriminals. We saw many new attacks going live, like typosquatting attack or event-stream incident , confirming that our ecosystem can be very fragile if we don’t build a stronger c…

## Indicators of Compromise (high-fidelity only)

- **MD5:** `c4fbb68607bcbb25407e0362dab0b2ea`

## MITRE ATT&CK Techniques

- **T1027** — Obfuscated Files or Information
- **T1204.002** — User Execution: Malicious File

## Kill chain phases observed

_(none detected from narrative keywords)_

## Recommended hunts

### Article-specific behavioural hunt — What is a backdoor? Let’s build one with Node.js

`UC_3092_1` · phase: **exploit** · confidence: **High**

**Splunk SPL (CIM):**
```spl
``` Article-specific bespoke detection — What is a backdoor? Let’s build one with Node.js ```
| tstats `summariesonly` count earliest(_time) AS firstTime latest(_time) AS lastTime
    from datamodel=Endpoint.Processes
    where (Processes.process_name IN ("node.js"))
    by Processes.dest, Processes.user, Processes.process_name,
       Processes.process, Processes.parent_process_name, Processes.process_path
| `drop_dm_object_name(Processes)`
| `security_content_ctime(firstTime)`
| append [
| tstats `summariesonly` count
    from datamodel=Endpoint.Filesystem
    where Filesystem.action IN ("created","modified")
      AND (Filesystem.file_name IN ("node.js"))
    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 — What is a backdoor? Let’s build one with Node.js
// Hunts the actual binaries / paths / commandline fragments named
// in the article instead of a generic technique-class template.
DeviceProcessEvents
| where Timestamp > ago(30d)
| where (FileName in~ ("node.js"))
| project Timestamp, DeviceName, AccountName, FileName,
          FolderPath, ProcessCommandLine,
          InitiatingProcessFileName, InitiatingProcessCommandLine
| order by Timestamp desc

// File-creation events for the named binaries / paths
DeviceFileEvents
| where Timestamp > ago(30d)
| where ActionType in ("FileCreated","FileModified")
| where (FileName in~ ("node.js"))
| 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.

- **File hash IOCs — endpoint file/process match** ([template](../_TEMPLATES.md#hash-ioc)) — phase: **install**, confidence: **High**
  - file hash IOC(s): `c4fbb68607bcbb25407e0362dab0b2ea`


## Why this matters

Severity classified as **HIGH** based on: IOCs present, 2 use case(s) fired, 2 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.