CEH V10 Scanning and Enumeration
Exam with Complete Solutions
ICMP Message Type 3 Codes - Answer-Error message followed by these codes:0 -
Destination network unreachable1 - Destination host unreachable6 - Network unknown7
- Host unknown9 - Network administratively prohibited10 - Host administratively
prohibited13 - Communication administratively prohibited
Port Scan Types - Answer-Full connect
Stealth
Inverse TCP flag
Xmas
ACK flag probe
IDLE Scan
Port Scan Full Connect - Answer-TCP connect or full open scan - full connection and
then tears down with RST Easiest to detect, but most reliable nmap -sT
Port Scan Stealth Type - Answer-Stealth - half-open scan or SYN scan - only SYN
packets sent. Responses same as full. Useful for hiding efforts and evading firewalls
nmap -sS
Port Scan Inverse TCP Flag - Answer-Inverse TCP flag - uses FIN, URG or PSH flag.
Open gives no response. Closed gives RST/ACK nmap -sN (Null scan) nmap -sF (FIN
scan)
Port Scan Xmas Scan - Answer-Xmas - so named because all flags are turned on so it's
"lit up" like a Christmas tree Responses are same as Inverse TCP scan Do not work
against Windows machines nmap –sX
LDAP Enumeration - Answer-Connects on 389 to a Directory System Agent (DSA)
Returns information such as valid user names, domain information, addresses,
telephone numbers, system data, organization structure and other items
Tools Softerra JXplorer Lex LDAP Admin Tool
NTP (Network Time Protocol) Enumeration - Answer-Runs on UDP 123
Querying can give you list of systems connected to the server (name and IP)
Tools NTP Server Scanner AtomSync Can also use Nmap and Wireshark
Commands include ntptrace, ntpdc and ntpq
SMTP (Simple Mail Transfer Protocol) Enumeration - Answer-VRFY - validates user
, EXPN - provides actual delivery address of mailing list and aliases
RCPT TO - defines recipients
Port Scan ACK Flag Probe - Answer-TTL version - if TTL of RST packet < 64, port is
open
Window version - if the Window on the RST packet is anything other than 0, port open
Can be used to check filtering. If ACK is sent and no response, stateful firewall present.
nmap -sA (ACK scan)
nmap -sW (Window scan)
Scanning Defintion - Answer-discovering systems on the network and looking at what
ports are open as well as applications that may be running
Connectionless Communication - Answer-UDP packets are sent without creating a
connection. Examples are TFTP, DNS (lookups only) and DHCP
Connection-Oriented Communication - Answer-TCP packets require a connection due
to the size of the data being transmitted and to ensure deliverability
TCP Flags - Answer--total of 8 bits for 8 flags
SYN (Synchronize) Set during initial communication. Negotiating of parameters and
sequence numbers ACK (Acknowledgment) Set as an acknowledgement to the SYN
flag. Always set after initial SYN
RST (Reset) Forces the termination of a connection (in both directions)
FIN (Finish) Ordered close to communications
PSH (Push) Forces the delivery of data without concern for buffering
URG (Urgent) Data inside is being sent out of band. Example is cancelling a message
TCP Handshake - Answer-SYN -> SYN-ACK - ACK
The protocol by which a client and server machine establish communication for the
transfer of data.
Internet Assigned Numbers Authority (IANA) - Answer-maintains Service Name and
Transport Protocol Port Number Registry which lists all port number reservations
Port 20/21 - Answer-FTP File Transfer Protocol (TCP/UDP) 21(SCTP)
Port 22 - Answer-SSH TCP
Port 23 - Answer-TCP Telnet
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