8、 Network security

The foundation of network security

Passive attack ： monitor （ Flow analysis ）, The prevention of , encryption

Take the initiative to attack ： counterfeit , replay , cheating , Tampering with news , Denial of service testing A firewall ,IDS

DOS attack   MAC Flooding,ARP Flooding,SYN Flooding

Modern encryption technology

Symmetric encryption algorithm 、 Shared key encryption algorithm

DES     64 Bit grouping secret key 56 position

3DES    Two keys   secret key 112 position

IDEA    64 Bit grouping   secret key 128 position

AES                secret key 128,192,256 position

RC4     Fast encryption ,WIFI scene

Asymmetric encryption algorithm 、 Public key encryption algorithm   RSA

Public key encryption , Private key decryption Confidential communications

Private key encryption , Public key decryption digital signature

digital signature

Confirm the sender's identity and message integrity

Message summary Hash hash

MD5  512 Bit grouping 128 Bit message summary

SHA  512 Bit grouping 160 Bit hash value

HMAC = Hash（ file +key）

The purpose of using message digest algorithm to generate message digest is to prevent the sent message from being tampered

Digital certificates and CA

digital certificate ：CA The private key ＋ Owner's public key

Certificate chain A obtain B The public key ： X1 《X2》 X2 《B》

  

VPN

Virtual private network Virtual Private Network

On the second floor PVN：L2TP、PPTP（ be based on PPP）

Three layers VPN：IPSec、GRE

four layers VPN：SSL

Realization VPN key technology ： Tunnel technology 、 Encryption and decryption technology 、 Key management 、 Authentication technology

Access/Remote VPN Realize user remote access

 

PPP The protocol and HDLC All protocols are link layer protocols

1. PPP Support upper layer multi protocol ,HDLC Only support IP
2. PPP Address negotiation ,HDLC no way
3. Both support error detection

PPP Protocol authentication function ：

PAP Two handshakes

CHAP Three handshakes , Pass on HASH value HMAC

IPSec

Three layers VPN Working in The network layer

Data integrity

authentication

confidentiality

Application transparent security

IPSec function ：

Certification head AH： Data integrity and data source authentication  MD5,SHA

Package safety load ESP： Data encryption  DES,3DES,AES

Internet Key exchange protocol IKE： Generate and distribute ESP and AH The key of

 

SSL and HTTPS

SSL（Secure Socket Layer） Secure socket layer , Transport layer Security protocols （ The fourth level ）, Realization Web Secure communications . be based on TCP port 443

SSL/TLS stay Web Secure communication is called HTTPS

application layer S-HTTP（Security HTTP）

Syntax and HTTP equally , Message headers are different

BGP Email security package , Provide data encryption and data signature .

IDEA Data encryption

RSA Public key certificate Authentication

MD5 Data integrity verification

S/MIME Email security services

SET E-commerce security

Kerberos Carry out identity authentication security protocol ,AAA： authentication （ Sign in ）, to grant authorization （ Get the ticket ）, Audit

A firewall

Intranet and extranet or intranet Different area isolation and access control

Packet filtering ACL（ The network layer ）, State FW（TCP Transport layer ）, Application layer gateway

IDS and IPS

Intrusion detection system is the second barrier behind the firewall Bypass deployment

Event generator ： Data collection

Event analyzer ： Pattern matching , Statistical analysis , Data integrity analysis

Classify according to data analysis technology and processing method ：

Anomaly detection ： Set the threshold , Can detect attacks that do not appear . Multiple false positives .

Misuse detection ： The accuracy of known intrusion detection is high , Highly dependent on feature library . Expert system and pattern matching

Intrusion prevention system IPS  Serial deployment

Hide internal network topology NAT

Computer virus and protection

System virus   Win32/95 infection exe,dll file

worm-type virus   Worm    Poison mail ,

Trojans   Trojan

Script virus   Script

Macro virus     Macro   infection Word Excel