Helpful first: IPsec VPNs: protecting a link you rent
Thirty days to Halcyon · Case 10: The flat network · Episode 4 of 7
Nyx, the Threat Hunter, walks Station South with a laptop and a roll of labels. There are three networks in the air.
One is SOUTH-. Its passphrase is printed on a label in the break room. Nyx labels everything, and did not make this one.
About sixty people know that passphrase. Two of them left last year. The control room desk phones use the same network. What could someone in the parking lot do with it?
By the end you can
- Order the four Wi-Fi security generations and say what broke the older ones
- Choose between personal and enterprise mode for a workplace network
- Protect voice calls and an SDN controller that share the data network
Four generations of Wi-Fi protection
A wall jack is inside the building. Radio is not. Wi-Fi sends every frame over shared spectrum, and it reaches the parking lot as easily as the control room. The protection has to be in the protocol itself. It has been rebuilt three times.
The first attempt was Wired Equivalent Privacy (WEP). It used the RC4 cipher with a very short 24-bit starting value and a checksum that was not cryptographic. Starting values repeat quickly, and an attacker can recover the key in minutes.
Wi-Fi Protected Access, or WPA, was a stopgap. It kept RC4 so that old hardware still worked, and added a protocol called TKIP. It is now deprecated. WPA2 replaced RC4 with AES, in a mode named CCMP.
WPA3 is the current generation. It fixes weaknesses that remained in WPA2, which the next section covers. One of Nyx's three networks, the one for printers, still uses WEP.
| Generation | Encryption | Status |
|---|---|---|
| WEP | RC4 with a static key, a 24-bit initialization vector, and a CRC-32 checksum | Broken. The key can be recovered in minutes through repeated initialization vectors. |
| WPA | RC4 with TKIP, the Temporal Key Integrity Protocol | Deprecated. An interim patch for legacy hardware. |
| WPA2 | AES-CCMP | The 4-way handshake in personal mode is open to offline dictionary cracking, and to the KRACK attack. |
| WPA3 | SAE handshake in personal mode. GCMP-256 in the 192-bit enterprise suite. | Current. Adds forward secrecy and mandatory protected management frames. |
PUT IT IN ORDER
Nyx's survey lists four kinds of Wi-Fi protection. Put them in order from oldest and weakest to newest.
- WPA2, with AES-CCMP
- WEP, with RC4 and a 24-bit initialization vector
- WPA, with RC4 and TKIP
- WPA3, with SAE and protected management frames
Show the answer
- WEP, with RC4 and a 24-bit initialization vector
- WPA, with RC4 and TKIP
- WPA2, with AES-CCMP
- WPA3, with SAE and protected management frames
WEP was broken first. WPA patched it on the same hardware. WPA2 moved to AES. WPA3 replaced the handshake that WPA2 personal mode left exposed.
One passphrase, or one identity each
WPA2 and WPA3 each come in two modes. Personal mode uses a pre-shared key, or PSK. That is one passphrase that everyone knows. Enterprise mode uses IEEE 802.1X and a RADIUS server. Each user or device signs in separately and gets its own session key.
A shared passphrase has an obvious problem at Station South. Sixty people know it, and two of them no longer work there. WPA2 personal mode has a less obvious one. A device joins through a 4-way handshake. An attacker can force a device to reconnect by sending it a forged deauthentication frame. The attacker records the handshake and then guesses passphrases against it offline, at any speed.
WPA3 personal mode replaces that handshake with Simultaneous Authentication of Equals (SAE). SAE blocks offline dictionary cracking. It also gives forward secrecy, so a passphrase learned later does not unlock traffic recorded earlier.
WPA3 also makes protected management frames mandatory. Forged deauthentication frames stop working. That matters because knocking a device offline is how an attacker pushes it onto an evil twin. An evil twin is a rogue access point that copies a real network's name.
Personal
- One passphrase for everyone
- PSK in WPA2, SAE in WPA3
- A leaver still knows it
- Fits a home or small office
Enterprise
- Each user or device signs in
- 802.1X with a RADIUS server
- Unique session key each
- Fits a workplace
SPOT THE PROBLEM
This is Nyx's survey of the air at Station South. Flag the lines that need fixing.
Show the answers
- SOUTH-OPS WPA2-Personal passphrase known to about 60 staff One shared passphrase, known to people who have left. Its handshake can be captured and cracked offline.
- SOUTH-PRINT WEP static key, set at install WEP is broken. The key can be recovered in minutes.
- (hidden) open note: safe because the name is hidden The name still appears in probe and association frames, and the network has no protection at all.
Voice and control on the same wires
Wi-Fi is one shared medium. The wired network has become another. A converged network carries voice, storage, and management traffic over the same IP network as everything else. Each kind of traffic then needs its own protection.
Voice over IP (VoIP) uses two protocols. Session Initiation Protocol, or SIP, sets up and ends calls. Real-time Transport Protocol, or RTP, carries the audio. Without encryption, calls can be overheard or hijacked. Kael Cho, Staff Infrastructure Engineer, has three fixes. He moves the phones to their own voice VLAN. He turns on SIPS, which is SIP over TLS, for call setup. He turns on Secure RTP, known as SRTP, for the audio.
Software-defined networking (SDN) splits a network's work into planes. The control plane is a central controller that makes the routing decisions. The data plane is the switches that forward packets. A management plane sits alongside them.
The controller is a single point of failure and a valuable target. Whoever controls it controls every switch. Its interfaces belong on a separate management network, and callers must authenticate with mutual TLS.
| Traffic | Risk | Protection |
|---|---|---|
| VoIP call setup, carried by SIP | Call hijacking and vishing | SIPS, which is SIP over TLS |
| VoIP audio, carried by RTP | Eavesdropping | SRTP |
| Phones on the same segment as laptops | Any compromised laptop can reach the phones | A dedicated voice VLAN. Block rogue DHCP and TFTP option injection. |
| SDN controller interfaces | Control of every switch from one place | An out-of-band management network, with mTLS on the northbound and southbound APIs |
SORT IT OUT
Kael lists four findings from the control room. Which protection answers each one?
Show the answers
- SRTP. RTP carries the audio. SRTP encrypts it.
- SIPS. SIP handles call setup. SIPS runs it over TLS.
- Voice VLAN. A dedicated voice VLAN separates the phones from other devices.
- Out-of-band management. The controller's interfaces belong on a separate management network, with mutual TLS.
CHECK YOUR JUDGMENT
About sixty staff share one WPA2 passphrase for Station South's operations Wi-Fi, and two of them have left Meridian. Vera Vance, your mentor, wants each device to sign in with its own identity and get its own session key. She also wants forged deauthentication frames to stop working. What should Kael deploy?
CASE FILE · CASE 10 · ENTRY 4 OF 7
Answer the closing question correctly to add this entry to your case file.
No passphrase to share
Station South Wi-Fi now signs in each device with its own certificate, so one leaked passphrase no longer opens the air to everyone.
Next episode: The network now knows which device is asking. It still takes a password's word for who.
Review sheet: exam notes and quick reference
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