Dynamic Host Configuration Protocol DHCP DHCP DHCP Discover
- Slides: 52
Dynamic Host Configuration Protocol DHCP
DHCP 동작과정 DHCP Discover DHCH Offer DHCP Request DHCP Ack
DHCP 취약점 DHCP DOS 공격 DHCP Starvation 공격 DHCP Spoofing 공격
DHCP DOS 공격
DHCP DOS 공격 �DHCP DOS 공격 DHCP DISCOVER DHCP RELEASE 반복적으로 보내어 DHCP Service를 무력화
DHCP DOS 공격 DHCP Discover DHCH Release Attacker DHCP Discover DHCH Release DHCP Server
DHCP DOS 공격 방어 � ip dhcp snooping Snooping기능 켜기 � ip dhcp snooping vlan 10 특정 vlan에서 snooping기능 작동 � ip dhcp snooping information option Relay agent 활성화 ▪ DHCP Reply는 Broadcast이므로 독립된 서브넷에 DHCP서버가 있는 경우 이 기능을 통해서 router를 통과하는 Broadcast Message 생성 � int fa 0/1 � ip dhcp snooping limit rate 100 해당 인터페이스에 서의 초당 최대 IP 요청 횟수를 제한
DHCP Starvation 공격
DHCP Starvation 공격 DHCP Discover 11: 11: 11: 11 DHCP Discover 11: 11: 11: 12 Attacker DHCP Discover 11: 11: 11: 13 DHCP Discover 11: 11: 11: 14 IP: 1. 1. 1. 2 IP: 1. 1. 1. 3 DHCP Server
DHCP Starvation 공격 방어 �ip dhcp snooping Snooping기능 켜기 �ip dhcp snooping vlan 10 특정 vlan에서 snooping기능 작동 �ip dhcp snooping trust 신뢰성이 있는 인터페이스를 trust 상태로 변환 Trust 상태인 포트에서 들어오는 DHCP 관련 Broadcast는 신뢰한다
DHCP Spoofing 공격
DHCP Spoofing 공격 �DHCP Rogue Server 1. 가짜 DHCP서버(Rogue Server)를 설치 2. DHCP DISCOVER 메시지 수신 3. DHCP OFFER를 가짜 DHCP서버가 보냄 4. Client가 Rogue 서버를 DHCP서버로 인식
DHCP Spoofing 공격
DHCP Spoofing 공격
DHCP Spoofing 공격
DHCP Spoofing 공격 방어 �ip dhcp snooping Snooping기능 켜기 �ip dhcp snooping vlan 10 특정 vlan에서 snooping기능 작동 �ip dhcp snooping trust 해당 인터페이스를 trust 상태로 변환 Trust 상태인 포트에서 들어오는 DHCP 관련 Broadcast는 통과시킴
DNS
DNS 취약점 DNS DNS Zone Transfer Dynamic Update 코드 취약점 Caching Poisoning
DNS Zone Transfer
DNS Zone Transfer 요청 Zone Data 전송 공격자의 DNS Server 위장 Secondary DNS Server 공격자 Primary DNS Server
DNS Zone Transfer 방어 �named. conf(/etc/named. rfc 1912. zones) allow-transfer { x. x; }; Zone 데이터를 획득할 수 있는 시스템 제한 Secondary 서버는 zone data를 넘길 일이 없으므 로 allow-transfer {none; }; 설정 � TSIG BIND-8. 2 이상 버전에서 지원 Zone 데이터에 대한 인증과 검증 Primary master name server와 slave name server에 암호 키를 설정 통신할 때 암호 키를 사용해서 인증
DNS Dynamic Update
DNS Dynamic Update DNS 변화 알림 DNS Update요청 거짓 정보 Update 위장 공격자의 Secondary DNS Server Primary DNS Client 공격자 Secondary DNS Server
DNS Cache Poisoning
DNS Address Spoofing “com” DNS Server IP : 2. 2 Root(”. ”) DNS Server 4. DNS Query “naver. com. ”? 3. “com. ” DNS Server = 2. 2 2. DNS Query “com. ”? Recursive Query Local DNS Server 5. “naver. com. ” DNS Server = 3. 3 6. DNS Query “café. naver. com. ” ? 7. “café. naver. com. ” = 4. 4 1. DNS Query “café. naver. com. ” DNS Client “naver. com” DNS Server IP : 3. 3
DNS Cache Poisoning “com” DNS Server IP : 2. 2 Recursive Query Root(”. ”) DNS Server Local DNS Server “naver. com” DNS Server IP : 3. 3 2. DNS Query “café. naver. com. ” 1. 가짜 cache 정보 전송 3. 잘못된 IP 주소 응답 Attacker DNS Client
DNS Address Spoofing “com” DNS Server IP : 2. 2 Root(”. ”) DNS Server 4. DNS Query “naver. com. ”? 3. “com. ” DNS Server = 2. 2 2. DNS Query “com. ”? Recursive Query Local DNS Server 5. “naver. com. ” DNS Server = 3. 3 6. DNS Query “café. naver. com. ” ? 7. “café. naver. com. ” = 4. 4 1. DNS Query “café. naver. com. ” DNS Client “naver. com” DNS Server IP : 3. 3
DNS Address Spoofing “com” DNS Server IP : 2. 2 Root(”. ”) DNS Server 4. DNS Query “naver. com. ”? 3. “com. ” DNS Server = 2. 2 2. DNS Query “com. ”? Recursive Query Local DNS Server 5. “naver. com. ” DNS Server = 3. 3 6. DNS Query “café. naver. com. ” ? “naver. com” DNS Server IP : 3. 3 7. “café. naver. com. ” = 4. 4 1. DNS Query “café. naver. com. ” Attacker DNS Client
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