Why construct a community monitor?
Not like the publicly accessible Wi-Fi community out there in airports, cafes, and sporting occasions, your property 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 threat, particularly if that password is additional shared. With the intention to assist himself extra rapidly establish unknown units, Donners got down to create a cheap community monitoring software that would alert him at any time when one thing connects.
A brief invoice of supplies
In comparison with different Wi-Fi community screens, or “pineapples” as they’re referred to as within the infosec career, this DIY model can be fairly barebones in each software program and {hardware} capabilities. On this iteration, Donners’ design is comprised of a single ESP32 as a consequence of its onboard Wi-Fi chip/antenna, and a USB energy provide.
Configuring the machine
Earlier than any scanning can start, the machine first has to know the place to attach, and that is completed by initially urgent a button linked to a digital IO pin which causes the ESP32 to create an entry level. As soon as linked, the configuration webpage presents a kind for coming into the goal entry level’s SSID, password, and timezone. Moreover, the person can add their Telegram API token and chat ID to realize entry to real-time alerts.
UDP packets
The person datagram protocol, or UDP, is an very simple communication protocol the place messages could be despatched with out the necessity for prior setup or additional error correction. Due to this, and together with IPv4, one can simply extract the sender’s IP deal with and the ports being accessed. However this solely supplies restricted data and could be despatched hundreds of instances a day from a single machine, due to this fact, Donners selected to solely choose DHCP packets since they’re despatched when a tool joins the community or must renew its IP deal with. They comprise the consumer’s MAC deal with, IP deal with, and optionally the hostname, amongst many different choices.
Telegram integration
With the Wi-Fi monitor now capable of acquire and parse DHCP packets into helpful data, Donners wished it to ship alerts through Telegram at any time when 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 machine by the chat, however customers are additionally capable of ship it instructions reminiscent of mute, unmute, and assist to simply management it with out the necessity for reprogramming or native community entry.
For extra data, you may watch Donners’ e14 Presents video under and view his code on GitHub.
