upstreamban

An upstreamban is a network traffic control mechanism used to block or restrict incoming connections to a server or network by targeting upstream servers or networks. Unlike traditional firewalls that filter traffic at the local level, an upstreamban specifically targets the source of the traffic, often the upstream provider or intermediary servers that relay malicious or unwanted connections.

This technique is commonly employed to mitigate distributed denial-of-service (DDoS) attacks, spam, or other forms of abuse. By blocking the upstream provider responsible for routing malicious traffic, administrators can effectively cut off a large volume of harmful requests at the source. This approach is particularly useful when the attacker’s IP addresses are dynamic (such as in botnet attacks) or when the attacker is using a large pool of compromised devices (e.g., in a botnet).

Upstreambans are typically implemented using tools like blackhole lists, BGP (Border Gateway Protocol) filtering, or DNS-based blocking. For example, an ISP or cloud provider may configure its routing tables to discard traffic originating from known abusive upstream networks. This method is more scalable than blocking individual IPs, as it prevents traffic from entire ranges or networks rather than single endpoints.

While effective, upstreambans can sometimes lead to collateral damage if legitimate traffic from the same upstream network is inadvertently blocked. Careful coordination with upstream providers and precise filtering rules are essential to minimize unintended disruptions. This technique is often used in conjunction with other mitigation strategies, such as rate limiting and traffic scrubbing, to provide comprehensive protection against network-based threats.