AS18136: the CTA JCOM Co., Ltd. network

AS18136 is an internet Autonomous System operated by CTA JCOM Co., Ltd. (Japan). Here is what that means and why this number may show up when you investigate a connection on your network.

What is AS18136?

An Autonomous System (ASN) is a block of networks under a single control with its own routing policy on the internet. The number AS18136 was assigned to CTA JCOM Co., Ltd. by an RIR (regional internet registry). All traffic entering or leaving that network is announced under this number.

Reach on the internet

AS18136 currently announces 3 IPv4 block(s), totaling about 43 thousand addresses (43,008 in all), registered in Japan. Services from CTA JCOM Co., Ltd. are reached through these addresses.

What it means to see AS18136 on your network

When you investigate where a connection from your computer or phone comes from (or goes to), you may find AS18136. That means the other end sits on the CTA JCOM Co., Ltd. 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.