A route leak or route hijack is what happens when BGP announcements send traffic somewhere it was never meant to go. They are among the most disruptive — and most common — internet incidents.
What it is
- A route leak occurs when a network advertises routes it shouldn’t, often by accident. Traffic that should have taken a short, direct path is suddenly funnelled through the wrong network, causing latency, congestion, packet loss, or a full outage for the affected destinations.
- A route hijack is when a network announces address space it doesn’t own — sometimes maliciously — so traffic destined for the rightful owner is diverted.
Because BGP largely trusts what it’s told, a single bad announcement can propagate widely in seconds and affect networks far from where the mistake was made.
Why it matters
Route leaks are not rare edge cases. High-profile incidents regularly knock out large parts of the internet: an operator accidentally leaking tens of thousands of prefixes, a submarine-cable operator’s leak taking a country’s connectivity offline, or a malformed announcement resetting sessions across major router platforms. For any organisation whose services, trading connectivity, or field sites depend on BGP, the risk is real and external — you can be affected by another network’s mistake.
What good looks like
You can’t prevent every upstream mistake, but you can detect and explain its effect on you fast. That means continuously watching the routes you receive and advertise, spotting when a prefix’s path or origin changes unexpectedly, and having the history to prove what happened and when — so you can escalate to the right provider with evidence instead of guesswork.