Course 14 - Wi-Fi Pentesting | Episode 5: WEP Cracking: Packet Injection and Replay Attacks (ARP, Chopchop, Fragmentation, and SKA)

In this lesson, you’ll learn about:Why WEP cracking depends on Initialization Vectors (IVs)How packet injection accelerates WEP crackingThe most reliable WEP injection technique (ARP Replay)Alternative injection methods for idle networksThe conceptual difference between Chopchop and Fragmentation attacksWhy Shared Key Authentication (SKA) changes the attack strategyHow attackers adapt when fake authentication is blockedForcing IV Generation on WEP Networks Cracking WEP depends on collecting a large number of Initialization Vectors (IVs). On busy networks, IVs are generated naturally through traffic. However, on idle networks, attackers must force the access point to generate new packets, which in turn generates new IVs. This episode explains three primary packet injection methods, followed by a special technique for Shared Key Authentication (SKA) networks. 1. ARP Request Replay Attack (Most Reliable Method) This is considered the most effective and dependable method for accelerating IV collection. Conceptual OverviewThe attacker monitors the network.A special ARP request packet is captured.This ARP packet is:Replayed repeatedly back into the network.Each replay forces the access point to:Respond with a new encrypted packetGenerate a new IVThis results in:A rapid increase in the IV countEnough data to crack:64-bit WEP keys128-bit WEP keysKey RequirementThe attacker must first associate with the target networkWithout association:The access point will ignore injected packets2. Chopchop Attack (For Low-Traffic Networks) This method is useful when:The network has no connected clientsThere is very little trafficNo ARP packets are naturally availableHow the Chopchop Attack Works (Conceptually)A single encrypted packet is captured.The attacker attempts to:Recover part of the keystreamEven a partial keystream (around 80–90%) can be sufficient.Using this partial keystream:A new forged ARP packet is created.This forged packet is then:Injected into the networkForces the access point to generate new encrypted packetsRapidly increases the IV countThis method:Does not rely on existing ARP trafficWorks even when the network is almost completely idle3. Fragmentation Attack This attack is similar in concept to Chopchop, but with an important difference. Key CharacteristicsInstead of recovering a partial keystream:The attacker recovers the entire 1,500-byte PRGAOnce the full PRGA is obtained:A forged packet is createdThe packet is injected into the networkIV generation increases rapidlyComparison with ChopchopRequires:Better signal qualityBeing physically closer to the access pointAdvantages:Much faster than ChopchopMore reliable once PRGA is fully obtained4. Cracking WEP Networks Using Shared Key Authentication (SKA) Most WEP networks use:Open AuthenticationHowever, some rare networks use:Shared Key Authentication (SKA)Why SKA Is DifferentIn SKA:The router refuses associationUnless the correct WEP key is already knownThis means:The standard fake authentication technique failsTraditional ARP replay cannot be initiated normallyModified ARP Replay Attack for SKA Networks To bypass SKA restrictions:The attacker must rely on:An already connected legitimate clientHow the Bypass Works (Conceptually)The attacker:Observes a connected clientTakes note of that client’s MAC addressThe ARP replay attack is then:Performed using the victim’s MAC addressThe access point believes:The traffic is coming from the authorized clientThis allows:Rapid packet generationIV collection without fake authenticationSuccessful WEP key recoveryThis method works for:SKA-based WEP networksStandard WEP networks as wellKey Educational TakeawaysWEP security fails because:IVs are too smallKeystreams get reusedPacket injection exists purely to:Speed up IV generationARP Replay is:The most reliable injection methodChopchop and Fragmentation are:Backup techniques for idle networksShared Key Authentication:Does not fix WEP’s cryptographic weaknessOnly changes the attack strategyYou can listen and download our episodes for free on more than 10 different platforms:https://linktr.ee/cybercode_academy