Lateral movement

Stage Loader

Stage Loader

Detection overview

The "Stage Loader" detection focuses on identifying initial payloads that are designed to download and execute additional malicious code. Stage loaders are typically small, lightweight programs that establish a foothold on a compromised system and then retrieve more complex and harmful payloads from a remote server. Detecting stage loaders is crucial as they are often the first step in a multi-stage attack, leading to the deployment of more sophisticated malware, data exfiltration, or further compromise.

Triggers

  • The detection results from the observation of two closed sessions where an internal host is attacking another internal host by uploading a payload which causes the destination host to connect back to the initial host to download additional stages of software

Possible Root Causes

  • The initial host is transmitting an exploit to a destination host which runs a stage loader and connects back to the initial host to load the rest of the malware necessary for the attacker to make progress toward their goal
  • Bidirectional transaction-based protocols where commands or requests are issued over one port/protocol and data is returned shortly thereafter over another port/protocol can also trigger the detection—common protocols which behave in this manner include the WinRM 2.0 Framework (used for Windows remote management), PostgreSQL, and SNPP (Simple Network Paging Protocol)

Business Impact

  • Lateral movement within a network expands an attacker’s footprint and exposes an organization to substantial risk of data acquisition and exfiltration
  • Lateral movement through exploits or leveraging stolen credentials is involved in almost all high-profile breaches
  • The destination host which is attacked provides a possible perspective on the potential business impact

Steps to Verify

  1. Determine whether there is any reason for the two hosts involved in a stage loading sequence to be communicating with each other
  2. Check to see whether any connections between the initial and destination host (in either direction) persist after the stage loading sequence
  3. Run all available endpoint checks on both the initial and the destination host to check for unwanted malware, but realize that fileless malware will typically escape detection
Stage Loader

Possible root causes

Malicious Detection

  • An attacker has delivered an initial payload designed to download additional malware.
  • Use of phishing emails, malicious websites, or drive-by downloads to deploy the stage loader.
  • Insider threat where an employee has intentionally introduced a stage loader into the network.
  • Benign Detection

  • Legitimate software updates or downloads that resemble stage loader activity.
  • Security assessments or penetration tests involving controlled deployment of stage loaders.
  • Misconfigured systems or applications generating unusual download and execution behaviors.
  • Stage Loader

    Example scenarios

    Scenario 1: An attacker sends a phishing email containing a link to a malicious website. The user clicks the link, and a small binary file is downloaded and executed. The detection is triggered by the unusual outbound network connection to a known C&C server and the execution of a new, unknown process.

    Scenario 2: During a penetration test, the security team uses a stage loader to simulate an initial malware delivery. The detection is triggered, and the activity is verified as part of the scheduled assessment.

    Stage Loader

    Business impact

    If this detection indicates a genuine threat, the organization faces significant risks:

    Further Compromise

    Stage loaders can download and execute more harmful payloads, leading to deeper infiltration.

    Data Exfiltration

    Subsequent payloads may focus on stealing sensitive data.

    Operational Disruption

    Malware downloaded by the stage loader can cause system instability, degradation of performance, or outages.

    Stage Loader

    Steps to investigate

    Stage Loader

    MITRE ATT&CK techniques covered

    FAQs

    What is a stage loader in the context of cybersecurity?

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    What steps should I take if I detect stage loader activity?

    How does Vectra AI detect stage loader activity?

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