Why construct a community monitor?
In contrast to the publicly accessible Wi-Fi community accessible in airports, cafes, and sporting occasions, your private home Wi-Fi community is meant to be secure. Nevertheless, as element14 Presents host Mark Donners factors out, offering the credentials to guests can create a danger, particularly if that password is additional shared. As a way to assist himself extra shortly establish unknown units, Donners got down to create a reasonable community monitoring instrument that would alert him every time one thing connects.
A brief invoice of supplies
In comparison with different Wi-Fi community displays, or “pineapples” as they’re known as within the infosec career, this DIY model could be fairly barebones in each software program and {hardware} capabilities. On this iteration, Donners’ design is comprised of a single ESP32 attributable to its onboard Wi-Fi chip/antenna, and a USB energy provide.
Configuring the gadget
Earlier than any scanning can begin, the gadget first has to know the place to attach, and that is achieved by initially urgent a button related to a digital IO pin which causes the ESP32 to create an entry level. As soon as related, the configuration webpage presents a type for getting into the goal entry level’s SSID, password, and timezone. Moreover, the consumer can add their Telegram API token and chat ID to realize entry to real-time alerts.
UDP packets
The consumer datagram protocol, or UDP, is an very simple communication protocol the place messages could be despatched with out the necessity for prior setup or further error correction. Due to this, and together with IPv4, one can simply extract the sender’s IP tackle and the ports being accessed. However this solely gives restricted info and could be despatched hundreds of instances a day from a single gadget, subsequently, Donners selected to solely choose DHCP packets since they’re despatched when a tool joins the community or must renew its IP tackle. They include the consumer’s MAC tackle, IP tackle, and optionally the hostname, amongst many different choices.
Telegram integration
With the Wi-Fi monitor now in a position to accumulate and parse DHCP packets into helpful info, Donners needed it to ship alerts through Telegram every time a tool joins the community. This was completed by organising a Telegram bot, getting the API token, after which organising a consumer within the ESP32 firmware. Not solely can the bot ship details about new gadget by the chat, however customers are additionally in a position to ship it instructions equivalent to mute, unmute, and assist to simply management it with out the necessity for reprogramming or native community entry.
For extra info, you possibly can watch Donners’ e14 Presents video under and view his code on GitHub.