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Update CEH Module 3 - Networks Scanning .md
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# TCP vs UDP
## TCP vs UDP
- TCP and UDP (Transmission Control Protocol and User Datagram Protocol) are communications protocol that facilitate the exchange of message (in form of Packets) between computer devices in a network. These protocols decide how packet will reach the destination. 65535
**TCP** **UDP**
- Connection Oriented Protocol - Connection Less protocol
- Provides Error checking - No Error Checking Mechanism
- Guarantees Delivery of Data - No Guarantees of Data Delivery
- Slower and less efficient for fast transmission - Faster Transmission
- All Packets follow the same path - Packets can follow any path to reach destination
- Automimic Retransmission possible - Retransmission is not possible
in case of Packets loss
TCP UDP
- Connection Oriented Protocol - Connection Less protocol
- Provides Error checking - No Error Checking Mechanism
- Guarantees Delivery of Data - No Guarantees of Data Delivery
- Slower and less efficient for fast transmission - Faster Transmission
- All Packets follow the same path - Packets can follow any path to reach destination
- Automimic Retransmission possible - Retransmission is not possible in case of Packets loss
---------------------------------------------------
## TCP Flags:
- **SYN** : Sync flag is used to Initiate 3 way handshake between hosts.
- **ACK** : Acknowledgment flag is used to acknowledge the successful receipt of a packet.
- **FIN** : The Finished flag means there is no more data from the sender. 1GB --> 50000 --> 1,2,3,4,5,6,.........50000 (FIN)
- **URG** : The Urgent flag is used to notify the receiver to process the urgent packets before processing all other packets.
- **PSH** : The Push flag is somewhat similar to the URG flag and tells the receiver to process these packets as they are received instead of buffering them.
- **RST** : Reset a Connection
- SYN : Sync flag is used to Initiate 3 way handshake between hosts.
- ACK : Acknowledgment flag is used to acknowledge the successful receipt of a packet.
- FIN : The Finished flag means there is no more data from the sender. 1GB --> 50000 --> 1,2,3,4,5,6,.........50000 (FIN)
- URG : The Urgent flag is used to notify the receiver to process the urgent packets before processing all other packets.
- PSH : The Push flag is somewhat similar to the URG flag and tells the receiver to process these packets as they are received instead of buffering them.
- RST : Reset a Connection
---------------------------------------------------
## TCP 3 Way Handshake:
| Client | Direction | Server |
|:---------:|:---------:|:---------:|
| SYN | ----> | |
| | <---- | SYN+ACK |
| ACK | ----> | |
######################################################################################################
## TASK ##
-------------------
# OSI Model
| Client | Direction | Server |
|:-------------:|:-------------:|:---------:|
| SYN | ----> | |
| | <---- | SYN+ACK |
| ACK | ----> | |

| Layer || Name || Description || Example protocols |
|:-----:||:------------------:||:..........................................:||:-----------------:|
| 7 || Application layer || Human Computer Interaction Layer. || HTTP, SNMP |
| 6 || Presentation layer || Ensure Data Usability Format || MIME, ASCII |
| 5 || Session layer || Maintain Con. and control Ports and Session|| SOCKS, NetBIOS |
| 4 || Transport layer || Data Transmission by TCP or UDP || TCP, UDP |
| 3 || Network layer || Decide Physical Path for Transmission || IP, ICMP |
| 2 || Data link layer || Read MAC Address from data packet || MAC, ARP |
| 1 || Physical layer || Physical connection || Ethernet, Wi-Fi |
-------------------------
# TCP/IP Model

| Layer | Name | Example protocols |
|:-----:|:------------------:|:-----------------:|
| 4 | Application layer | HTTP, SNMP |
| 3 | Transport layer | TCP, UDP |
| 2 | Internet layer | IP, ICMP |
| 1 | Link layer | ARP, MAC |
-------------------------
# TCP vs UDP
How is TCP different from UDP and how packets are delivered to target.
###############################################################################################################
## OSI Model
_________________________________________________________________________________________________________
| Layer || Name || Description || Example protocols |
|:-----:||:------------------:||:----------------------------------------------:||:--------------------:|
| 7 || Application layer || Human Computer Interaction Layer. || HTTP, SNMP |
| 6 || Presentation layer || Ensure Data Usability Format || MIME, ASCII |
| 5 || Session layer || Maintain Con. and control Ports and Session || SOCKS, NetBIOS |
| 4 || Transport layer || Data Transmission by TCP or UDP || TCP, UDP |
| 3 || Network layer || Decide Physical Path for Transmission || IP, ICMP |
| 2 || Data link layer || Read MAC Address from data packet || MAC, ARP |
| 1 || Physical layer || Physical connection || Ethernet, Wi-Fi |

## TCP/IP Model
__________________________________________________
| Layer | Name | Example protocols |
|:-----:|:------------------:|:-----------------:|
| 4 | Application layer | HTTP, SNMP |
| 3 | Transport layer | TCP, UDP |
| 2 | Internet layer | IP, ICMP |
| 1 | Link layer | ARP, MAC |
---------------------------------------------------------------------------------------------------------------
# Practical Part
------------------
# Main Objectives
k1. **Scan live host**
k2. **Open Ports and Running Services**
k3. **OS and Architecture info**
k4. **Security Implemented (Firewall, IDS, IPS) Detection and evasion**
## Main Objectives
k1. Scan live host
k2. Open Ports and Running Services
k3. OS and Architecture info
k4. Security Implemented (Firewall, IDS, IPS) Detection and evasion

# k1. Live hosts
## k1. Live hosts
arp-scan --local
nmap -sn <network>/<cidr> -sn specify NO-Port Ping Scan
ping <ip>
netdiscover -r <network address>/<cidr>
--------------------------------------------------------------------------
# Nmap Port Scan Status
## Nmap Port Scan Status
Open - If No response is received by Nmap, it means Port is Open for connection.
Closed - If response is received by nmap with RST or SYN flag, it means ports are closed.
Filtered - May be some kind of firewall is implemented on client side.
Open/Filtered - Nmap is confused, either port is open or filtered.
Closed/Filtered - Nmap is confused, either port is closed or filtered
--------------------------------------------------------------------------
# k2. Open Ports and Running Services Scan
**Nmap**
nmap <ip> Simple Port Scan
nmap -v <ip> Port Scan with increase verbosity. (-vv is more powerful)
nmap <ip> <ip> <ip> Scan Multiple host in single go
nmap <1.1.1.2-200> Scan IP Range from 2 to 200
nmap <network>/cidr Scan Entire Subnet
nmap -p 1-65535 <ip> -p specify Port Numbers to scan.
nmap -p U:<port>,T:<port> <ip> Scan specified TCP and UDP ports. use "*" for all.
nmap -sU <ip> Scan 1000 Common UDP Ports
nmap -T<0-5> <ip> -T specify intensity of scan to time taken by scan. 5 is
fastest and 0 is slowest. Default Speed is 3(-T3).
nmap -sT <ip> TCP Connect Scan
nmap -iL list.txt scan ip written in list.txt file (Separate IP by Space, Tab or New Line). --exclude file list.txt (to exclude ip from search)
nmap -A <ip> Aggressive Scan (it use -O -sC --traceroute -sV) options
nmap -O <ip> -O is used for OS Detection
nmap -sC <ip> -sC is used to run Default NSE Scripts --- **--script**
nmap -sV <ip> -sv is used for Service Version Detection
nmap -6 <ip> IPv6 Scan
nmap -sS <ip> Sync Scan/Ping. Helpful in case where ICMP pings are blocked.
nmap -sA <ip> ACK Scan/Ping. Helpful in case where ICMP pings are blocked. Null Scan
nmap --scanflags SYNACKFIN <ip> We can set flags using --scanflags option.
nmap -Pn <ip> Don't Ping Scan (When Firewall block Ping Packets)
nmap -sR <ip> Scan for RPC (Remote Procedure Call) Service
**Hping3**
hping3 --icmp <ip> --verbose Ping Scan in Verbose
hping3 --scan <ports> <ip> Scan for Open Ports on IP (--ack, --syn, --fin, --urg)
hping3 --udp <ip> --verbose UDP port Scan in Verbose
--------------------------------------------------------------------------
# k3. OS Detection
nmap -O <ip> OS Detection with Nmap
--------------------------------------------------------------------------
# k4. Security Implemented (Firewall, IDS, IPS) Detection and evasion
nmap -f <ip> -f will fragment packets in 8-byte packets. Helpful when
attempting to evade some older or improperly configured
firewall or we can specify packet fragment size using
--mtu <size>" option. Size should be multiple of 8
## k2. Open Ports and Running Services Scan
Nmap
nmap <ip> Simple Port Scan
nmap -v <ip> Port Scan with increase verbosity. (-vv is more powerful)
nmap <ip> <ip> <ip> Scan Multiple host in single go
nmap <1.1.1.2-200> Scan IP Range from 2 to 200
nmap <network>/cidr Scan Entire Subnet
nmap -p 1-65535 <ip> -p specify Port Numbers to scan.
nmap -p U:<port>,T:<port> <ip> Scan specified TCP and UDP ports. use "" for all.
nmap -sU <ip> Scan 1000 Common UDP Ports
nmap -T<0-5> <ip> -T specify intensity of scan to time taken by scan. 5 is fastest and 0 is slowest. Default Speed is 3(-T3).
nmap -sT <ip> TCP Connect Scan
nmap -iL list.txt Scan ip written in list.txt file (Separate IP by Space, Tab or New Line). --exclude file list.txt (to exclude ip from search)
nmap -A <ip> Aggressive Scan (it use -O -sC --traceroute -sV) options
nmap -O <ip> -O is used for OS Detection
nmap -sC <ip> -sC is used to run Default NSE Scripts --- --script
nmap -sV <ip> -sv is used for Service Version Detection
nmap -6 <ip> IPv6 Scan
nmap -sS <ip> Sync Scan/Ping. Helpful in case where ICMP pings are blocked.
nmap -sA <ip> ACK Scan/Ping. Helpful in case where ICMP pings are blocked. Null Scan
nmap --scanflags SYNACKFIN <ip> We can set flags using --scanflags option.
nmap -Pn <ip> Don't Ping Scan (When Firewall block Ping Packets)
nmap -sR <ip> Scan for RPC (Remote Procedure Call) Service
Hping3
hping3 --icmp <ip> --verbose Ping Scan in Verbose
hping3 --scan <ports> <ip> Scan for Open Ports on IP (--ack, --syn, --fin, --urg)
hping3 --udp <ip> --verbose UDP port Scan in Verbose

nmap -D RND:<val> <ip> -D Decoy option is used to mask an Nmap scan by using one
or more decoys. Decoy is used to hide identity. RND is
Number of Decoy Address to be used. We can also specify
Addresses by our own. as
nmap -D decoy1,decoy2,decoy3,etc <ip>

nmap -sX <ip> Nmap XMas Scan (if Firewall is enable you get
(all thousand ports are closed/filtered), if Firewall is
disable you get (Closed). Xmas Scan use PSH+URG+FIN flag
or All flag for packets and create abnormal situation for
client for which client either respond with RST Flag or
some relevant info.
--------------------------------------------------------------------------
--------------------------------------------------------------------------
# We can also use Zenmap
## k3. Security Implemented (Firewall, IDS, IPS) Detection and evasion
nmap -f <ip> -f will fragment packets in 8-byte packets. Helpful when attempting to evade some older or improperly configured firewall or we can specify packet fragment size using --mtu <size>" option. Size should be multiple of 8
nmap -D RND:<val> <ip> -D Decoy option is used to mask an Nmap scan by using one or more decoys. Decoy is used to hide identity. RND is Number of Decoy Address to be used. We can also specify Addresses by our own. as nmap -D decoy1,decoy2,decoy3,etc <ip>
nmap -sX <ip> Nmap XMas Scan (if Firewall is enable you get (all thousand ports are closed/filtered), if Firewall is disable you get (Closed). Xmas Scan use PSH+URG+FIN flag or All flag for packets and create abnormal situation for client for which client either respond with RST Flag or some relevant info.
--------------------------------------------------------------------------
## We can also use Zenmap
--------------------------------------------------------------------------

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