Communication & Network Security Flashcards
Decimal
10
Binary
2
Hex
16
Protocol
Agreed upon set of rules
Defines the format and order of messages and actions taken upon receipt of the message
Encapsulation
Layered model (OSI)
OSI Layer
Please Do No Throw Sausage Pizza Away (Bottom to Top) Application Presentation Session Transport Network Data link Physical
Application Layer
interacts with applications to determine which network service will be required.
Layer 5-7 - considered Data Layers
Presentation Layer
data sent from one side of the connection is received Presenting data to application (Characters set/ graphics) in a way that makes sense
Layer 5-7 - considered Data Layers
Session Layer
establish and maintains connection between systems
Layer 5-7 - considered Data Layers
Transport Layer
ensure transmission end to end
handles sequencing of packets in transmission
Port/TCP & UDP headers
Network Layer
interaction network address schemes
How different network segment interact with each
other
IP Address/Routing
Data Link Layer
connects physical layer to network Ethernet address (MAC)/switches
Physical Layer
transmission across physical media
Bits 0/1
TCP/IP Model
Layer 5-7 (Application)
Layer 4 - Host to Host transport
Layer 3 - Internet
Layer 1-2 Network Access
TCP/IP Protocol Stack
Developed 1970, Darpa, DOD
OSI still referenced when talking about layers
IP4 Packets Diagram
32 bits across. Every 32 bit is 4 bytes. 5 rows so total of 20 bytes Starts at 0 Bits 0-31 Bytes 0-19
IP4 Class Address
Classless Inter-Domain Router (CIDR) (/8 notation)
Class A: /8 - 1.0.0.0 to 127.255.255.255
Class B: /16 - 128.0.0.0 to 191.255.255.255
Class C: /24 - 192.0.0.0 to 223.255.255.255
Class D: Multicast
Class E: Reserved
IP Broadcast
Limited broadcast (no router will block ) 255.255.255.255 Direct broadcast - 192.168.1.255 - Broadcast from 192.1.168.0 network
RFC-1918 (think of NAT)
Private addresses
- 0.0.0/8
- 16.0.0/16 - 172.31.0.0/16
- 168.0.0/16
Network Address Translation (NAT)
one to one -
Pool NAT - maps to a set of public addresses
Many to one - multiple mapped to one
NAT limitation 64k
gethostbyname
have fully qualified domain name (eric.sans.org) and need the address
gethostbyaddr
when you have address and the need the fully qualified domain name
DNS request & response
UDP if under 512 bytes
DNS Security issues
Not reliable
DNS Poisoning Attack
DNSSEC
does not provide confidentiality
digital signature for packet
Authenticated Denial of Existence (DNS)
Proving DNS record does not exist
IPv6
IPv4 - 32 bit 4.2 billion unique addresses
IPv6 - 128bit 340 undecillion addresses
Faster, no checksum like IPv4
IPv6 Features
route aggregation - method used to minimize the number of routing tables required in an IP network.
Support IPv6 tunneling over IPv4
Fixed header bytes - next header
Auto-configuration - don’t need to assign IP address
User Datagram Protocol (UDP)
Layer 4 connection less communication don't care if the packet gets there less overhead Good if small amount of packet loss is acceptable
UDP Ports
DNS 53
NTP - 123
BootP - 67 & 68
SNMP - 161
Transmission Control Protocol
3 way handshake
SYN
SYN-ACK
ACK
TCP Header (Key fields)
Source Port Destination Port Sequence number Acknowledgement number SYN bit ACK bit
TCP Ports
20 - FTP Data (receive) 21 - FTP - (send) 22 - SSH 23 - Telnet 25 - SNMP 53- DNS 79- Finger 80 - http 443 - https source port >= 1024 (ephemeral)
TCP Code Bit (Flags)
Urg (Urgent) Ack (Acknowledgement) PSH (Push) - think of data stream RST (Reset) - terminate connection SYN(Synchronize) FIN(Finish)
TCP Port Scanning (response types)
SYN/ACK - port is open and unfiltered
RST/ACT - port is closed and unfiltered
No response: Unknown
Socket Pair
Source IP Address
Source Port number
Destination IP Address
Destination Port Number
Internet Control Message Protocol (ICMP)
report error (troubleshoot) rather than transfer info Ping & Traceroute are ICMP
TraceRoute
Set TTL to 1 and when router receives it, it will drop it.
Next iteration - TTL decreases for the one below it
Incrementing TTL for each hop
Secure Shell (SSH)
Port 22
Supports Authentication, compression, confidentiality, and integrity
Supports wide range of ciphers, 3DES, AES, Blowfish
SSH1 - Man In the middle attack
Secure Multipurpose Internet Mail Extension (S/MIME)
Secure MIME
Simple Network Management Protocol (SNMP)
Monitoring of network devices SNMPv1 and SNMPv2 - clear text community string (NO CONFIDENTIALITY) Public - read Private - read & write Should use SNMPv3 - port 161
Multilayer Protocols
TCP/IP - span multiple layers (OSI)
DNP3 (Distributed Network Protocol)
DNP3 (Distributed Network Protocol)
Open protocol smarts Smart Grid SCADA IEEE 1815- 2010 allowed pre-share key only IEEE 1815 - 2012 current standard Supports PK
Network Attached Storage (NAS)
Read/Write entire files
Storage Area Network (SAN)
block/clusters to files (not entire files like NAS)
Internet Small Computer System Interface (ISCSI)
network cables/routed via IP (NAS)
think of SCSI drives that are connected to network
Lun - logical grouping of drives
Fibre Channel
Sans Protocol
Does not use Ethernet/does not easily scale across WAN
Fibre Channel (FCoE)
Local subnet only
TCP/IP is not used - layer 2
Fibre Channel over IP (FCIP)
can route (layer 3)
Voice of IP (VOIP)
Digitized before sending across wire Combining data Cost-effective Redundancy Security issue (PBX) Expsoures
PSTN PBX/VOIP
Common and phased approach
PBX and VOIP network
UP PBX/PSTN
must use VOIP phones
IP PBX - soft switch route calls