Network Security: DoS Flashcards
What is a DoS attack?
Definition according to NIST:
The prevention of authorized access to resources or the delaying of time-critical operations
DoS attacks seeks to compromise the availability of a service.
How can DoS attacks be carried out on the physical layer? (OSI layer 1)
Network wires and such can be destroyed or tampered with physically.
In the lecture, an example was used where construction work on a highway caused internet and phone disruptions.
What is the most common form of DoS attacks against wireless networks?
Drowning out the legitimate signals with noise. This is also called jamming.
What is the hidden terminal problem?
A problem where nodes can communicate with a wireless access point, but not directly with other nodes that might also use this access point.
Node A and C and see node B, but not each other.
This can result in interference.
What is SIFS and DIFS?
(Short Interframe Spaces and
Distributed Coordination Function Interframe Spaces)
Safeguards against collisions. Often used in 802.11. Adds gaps in-between packets.
SIFS is used for existing exchanges and DIFS is required for new exchanges.
What is RTS/CTS?
Request to Send / Clear to Send.
Reservation mechanism where you ask for allowance before communicating over wireless networks. The receiving node will defer all other transmissions for the requested time. Helps prevent collisions.
How can RTS/CTS be abused by attackers?
An attacker can modify the duration field of the RTS packets to reserve the channel for additional time.
The maximum time is 32,767 ms, meaning that a rogue station can block all other stations by sending malicious RTS 30 times per second.
The attack can be carried out with minimal equipment. A Raspberry Pi is sufficient.
What is a deauthentication attack?
An attack that uses a feature of the 802.11 standard to achieve DoS.
802.11 allows base stations to disassociate rogue stations by sending a disassociation frame. They are not authenticated and cannot be refused.
To carry the attack out, the attacker needs to know the MAC address of the victim. MAC address can be found by sniffing wireless network.
