Port 5555: Android Debug Bridge
Port 5555 is Android Debug Bridge over the network, which gives full developer control of an Android device.
What runs on port 5555
ADB is the developer tool for installing apps, running shell commands and debugging Android devices. When network debugging is enabled, the device listens on TCP 5555 and accepts commands from any computer that connects, subject to an authorisation prompt on devices that support it.
On a home network
Android TV boxes, Fire TV sticks with ADB debugging on, some cheap Android set-top boxes and developers' phones may listen on 5555. Some low-cost TV boxes have shipped with it enabled.
If port 5555 is reachable from the internet
5555 should never be reachable from the internet. In 2018 the ADB.Miner worm spread across internet-exposed Android devices, mostly TV boxes, installing cryptominers through open ADB, and later botnets have done the same. On a device without the authorisation prompt, anyone who connects gets a shell.
How to check whether it is open on your network
On Android and Fire TV, turn off ADB and network debugging in Developer Options when you are not using them. A LAN port scan will show which devices have 5555 open.
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