Firewall (only one feature, firewall never blocks a website, either it will allow a port, or disallow a port) 

IDS (INtrusion Detection SYstem) : A log, IR team montiors the traffic, rules were generated accordingly.

IPS (Intrusion Prevention System): Capability of logging, rules can be generated automatically.  Next Generation firewall.

Firewall Architecture:

Bastion Host:refer to 2Bastion.jpg
 
ScreentSubnet: Refer to 3Subnet.jpg (DMZ)

Multihome: Refer to 4multi.jpg


Firewall Types: Refer to firewall type.jpg


Packet Filter Firewall: Refer to 6packet.jpg (OPerates at Network Layer)


Circuit Level Gateways: Refer to 7circuit.jpg (OPerates at Session Layer of OSI Model)

Application Level Gateways: Refer to 8application.jpg (Operates at Application Layer of OSI Model)

Stateful Multilayer Packet inspection firewall: Refer to 9stateful.jpg (Operates at Network Layer of OSI model)

OSI:
refer to 
tenosi.jpeg


Cryptography

conversion of data, into a scrambled code, that is encrypted and send accross public or private network.

2 types:

Symmetric and Assymetric

Symmetric: Uses same key for both encryption and Decryption

Assymetric: Uses public and private key encryption.

DES: Data Encryption Standard. 

symetric Key , 56 bit key

AES : Advance Encryption STandard

Symmetric Key Encryption: 128 bit:

RSA: Rivesh, shammir, Addleman

Assymetric Key Encryption, Uses Prime number for factorization:

MD: Message Digest:

128 to 256 bit length key size. MD5 most popular

successor                                                           telnet ---> SSH, ssl ---> tls ,ftp --> sftp
SHA1  - 160 bit digest. it resembles like MD5.

SHA2  - 256 bit digest.  

SHA3  - 264 bit digest. 

PKI:  refer to pki.jpg