SNMP GetBulk Reflected Distributed Denial of Service Attack

Understanding SNMP and GetBulk

SNMP (Simple Network Management Protocol) is a widely used protocol for network management and monitoring. It allows administrators to access and manage network devices, such as routers, switches, and servers. SNMP GetBulk requests allow the retrieval of a large amount of data from multiple network devices in a single request, resulting in increased efficiency and reduced network traffic. This is a boon for network administrators, making their jobs easier. But it is a boon for threat actors, as well.

SNMP GetBulk Reflected DDoS Attack

Threat actors can take advantage of the SNMP GetBulk command's ability to retrieve a large volume of data from multiple devices simultaneously. They exploit this capability by reflecting and amplifying the attack traffic off SNMP enabled devices, creating significantly larger traffic volumes than the attacker's resources alone could generate. This is commonly known as a Reflected Distributed Denial of Service (Reflected DDoS) attack.

The attackers send spoofed requests with the victim's IP address as the source to various SNMP-enabled devices on the network. These devices, often routers or switches, then respond to the requests by sending large amounts of data to the victim's IP address. Since the volume of data requested can be disproportionately greater than the small requests sent by the attacker, the victim's network infrastructure becomes overwhelmed, resulting in denial of service to legitimate users and system instability.

Dangers and Impacts

  1. Network Congestion: The SNMP GetBulk Reflected DDoS attack floods the victim's network, causing significant congestion, network latency, and reduced performance. Legitimate users may experience slow response times or even complete service interruptions.
  2. Infrastructure Overload: The attack consumes the resources of networking infrastructure elements, such as routers and switches, overwhelming them with excessive data transmissions. This overload can lead to system crashes or unresponsiveness, affecting critical network services.
  3. Bandwidth Exhaustion: The massive influx of spoofed requests, combined with the amplified responses from SNMP-enabled devices, consumes significant network bandwidth. As a result, available bandwidth is exhausted, crippling the victim's ability to handle legitimate network traffic.

Prevention and Mitigation

To protect your organization's network infrastructure from SNMP GetBulk Reflected DOS attacks, consider implementing the following measures:

  1. SNMP Access Control: Disable SNMP access from untrusted sources and restrict SNMP exposure strictly to the necessary devices. Utilize strong authentication mechanisms such as SNMPv3, which includes support for encrypted communication.
  2. Network Segmentation: Apply proper network segmentation to minimize the impact of potential attacks. This prevents attackers from directly reaching critical network infrastructure components.
  3. Network Monitoring: Employ comprehensive network monitoring tools capable of detecting abnormal SNMP traffic patterns, allowing early identification and response to potential attacks.
  4. Firewall Configuration: Configure firewalls to block suspicious or spoofed SNMP requests, limiting their ability to reach SNMP-enabled devices.
  5. Regular Updates and Patching: Ensure that all SNMP-enabled devices have the latest firmware or software updates, as vendors frequently release patches to address security vulnerabilities.
  6. Default Community Strings: The default SNMP community strings of “private” for read/write access and “public” for read-only access should be changed. These strings are well known and should be changed to something unique and not easily guessed.


SNMP GetBulk Reflected DDoS attacks pose a significant threat to network infrastructure. Organizations must remain vigilant and take proactive steps to secure their networks. By implementing robust access controls and network segmentation, businesses can greatly reduce the chance of an attack like this occurring. With the help of continuous monitoring, businesses can mitigate the impacts of the attack and ensure uninterrupted network services for their users.