AS131989: the PFU-UMC-MS01 PFU LIMITED network

AS131989 is an internet Autonomous System operated by PFU-UMC-MS01 PFU LIMITED (Japan). Here is what that means and why this number may show up when you investigate a connection on your network.

What is AS131989?

An Autonomous System (ASN) is a block of networks under a single control with its own routing policy on the internet. The number AS131989 was assigned to PFU-UMC-MS01 PFU LIMITED by an RIR (regional internet registry). All traffic entering or leaving that network is announced under this number.

Reach on the internet

AS131989 currently announces 1 IPv4 block(s), totaling 256 addresses (256 in all), registered in Japan. Services from PFU-UMC-MS01 PFU LIMITED are reached through these addresses.

What it means to see AS131989 on your network

When you investigate where a connection from your computer or phone comes from (or goes to), you may find AS131989. That means the other end sits on the PFU-UMC-MS01 PFU LIMITED network (Japan). It can be legitimate — a cloud service, an ISP, a CDN — or an unexpected connection worth checking.

How to see every connection and network your devices reach

Tracing one connection's ASN at a time is tedious. Sentinela, by PC Monitor, maps the devices on your network, shows what is exposed to the internet and helps flag suspicious connections and devices — running on your Windows. Meet Sentinela.