Rpcdcom

Overview

Exploit:Win32/Rpcdcom is an extremely critical vulnerability detection that identifies attempts to exploit the notorious **MS03-026** vulnerability in the Microsoft RPC (Remote Procedure Call) DCOM interface. This specific exploit is infamous because it was the primary propagation vector for the devastating **Blaster** (and Nachi) worms in 2003, which caused billions of dollars in damage globally.

Understanding Rpcdcom (MS03-026)
To an end-user, a successful exploit often results in the system repeatedly and unexpectedly restarting with an error message about `NT AUTHORITY\SYSTEM`. For a network administrator, an Rpcdcom alert indicates that an unpatched machine is under active attack, or worse, that a worm is actively scanning and propagating within the internal network (`T1210`). The vulnerability allows for unauthenticated Remote Code Execution (RCE) at the SYSTEM level.

Execution and Exploitation Mechanics
The attacker or worm sends a specially crafted, oversized packet to port 135 (the RPC Endpoint Mapper) on the target machine. This triggers a buffer overflow in the RPC DCOM interface (`T1190`), allowing the attacker to inject and execute arbitrary shellcode in the context of the `SYSTEM` account (`T1068`). Once the shellcode executes, it typically drops a secondary payload (like `msblast.exe`) and initiates a TFTP (`T1105`) transfer to pull down the rest of the worm's components, establishing persistence and beginning to scan for new targets.

Indicators of Compromise & Impact
The impact is total, unauthenticated system compromise. Network IoCs include a massive spike in traffic on TCP port 135 (RPC) and UDP port 69 (TFTP). Host-based IoCs include the unexpected termination of the `svchost.exe` process (which hosts the RPC service), resulting in the classic 60-second shutdown timer. The presence of files like `msblast.exe` or `teekids.exe` in the `System32` directory is a definitive indicator.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to the MITRE ATT&CK framework:

Generated Detections (Boilerplate)

These YARA and Sigma rules are auto-generated based on the family name and aliases. They must be heavily tuned before deployment in a production environment.

YARA Rule

rule MALWARE_WIN_RPCDCOM {
    meta:
        description = "Detects Rpcdcom (advanced_threat)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "rpcdcom" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Rpcdcom Activity
id: 9c700370655808485b905034126b2e0b
status: experimental
description: Detects generic indicators of the rpcdcom malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*rpcdcom*"
    condition: selection
level: medium

Containment & Response Steps

Ordered checklist for responders. Adapt to your environment and engage professional support for active incidents.

1. Immediately disconnect the affected machine from the network; if it is infected with Blaster, it is actively attacking other systems.
2. Apply the MS03-026 security patch (and all subsequent Windows updates) immediately.
3. Block TCP port 135 and UDP port 69 (TFTP) at the network perimeter firewall to prevent external exploitation and inbound payload transfers.
4. Run a dedicated removal tool for the Blaster worm to clear the registry persistence and remove the malicious executables.

What to Avoid

Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.

1. Do not connect an unpatched legacy system (like Windows XP or 2000) directly to the internet without a hardware firewall blocking port 135.
2. Avoid assuming the network is safe just because the worm was removed; you must apply the patch or it will be reinfected instantly.

References & External Analysis

• Search "rpcdcom" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: advanced_threat)

Explore other malware families in the same category:

• Monder
• Downloadassistant
• Ngrbot
• Alyak
• Simpleregistrycleaner

Machine-readable

Get this profile as JSON: https://jordan123234-malware-families-explorer.static.hf.space/api/rpcdcom.json

Ecosystem & Interactive Environments

This profile is part of the Malware Families Catalog, a public dataset of 2,899 malware families. The catalog is also published across our ecosystem: Hugging Face, Kaggle, Zenodo, Replit, StackBlitz, CodeSandbox, and CodePen.