Google services were temporarily unreachable for some users after some traffic intended to reach the web giant was rerouted through other networks.

In a notice posted on Monday on its website, Google said it had resolved the issue as of 2:35 p.m. Pacific Standard Time, and that its services were operating as expected. The Alphabet Inc. unit said it would conduct an internal investigation but that it believed the root cause of the issue was external to Google.

Internet research firm ThousandEyes said incorrect routing instructions redirected some traffic intended for Google’s addresses to Russian network operator TransTelekom, China Telecom Corp. and MainOne, a provider in Nigeria.

“All of Google’s public-facing edge seems to be getting broadly affected,” ThousandEyes marketing executive Alex Henthorne-Iwane said. “Most of the traffic is being dropped at China Telecom.”

On Twitter and online forums, some users complained that they couldn’t access Google’s services, but the scope of the outage wasn’t clear.


A Google spokesman said Monday that there was no compromise of Google’s services and that the company has no reason to believe that the incident was malicious. Almost all of Google’s traffic is encrypted and would not have faced a greater risk of being exposed due to the incident, he said.

Facebook Inc. on Monday also experienced an unrelated outage that the company attributed to a routine test.

Network engineers have warned for years that online platforms are vulnerable to network-based attacks that send data widely off course. Such attacks are possible because large network-service providers exchange traffic through a system that is largely based on mutual trust through protocols nearly as old as the internet itself.

Failures such as the one Google experienced on Monday can occur because of a technical error—when a network engineer misconfigures systems, for example—or they could also represent a malicious attempt to intercept data, network experts say.


If they have access to a large enough network operator, hackers can alter network maps stored on core internet routers through a system known as border gateway protocol, or BGP. Using BGP flaws to reroute data could let a hacker steal information, eavesdrop on traffic or send information into cyber oblivion, security researchers say.

Write to Drew FitzGerald at andrew.fitzgerald@wsj.com and Robert McMillan at Robert.Mcmillan@wsj.com