Network Security - secuguru/security-terms GitHub Wiki

  • OSI (Open Systems Interconnection) Model

    • Application; layer 7 (and basically layers 5 & 6) (includes API, HTTP, etc).
    • Transport; layer 4 (TCP/UDP).
    • Network; layer 3 (Routing).
    • Datalink; layer 2 (Error checking and frame synchronisation).
    • Physical; layer 1 (Bits over fibre).

  • Firewall

    • Rules to prevent incoming and outgoing connections.

  • NAT (Network Address Translation)

    • Useful to understand IPv4 vs IPv6.

  • DNS (Domain Name System)

    • (53)
    • Requests to DNS are usually UDP, unless the server gives a redirect notice asking for a TCP connection. Look up in cache happens first. DNS exfiltration. Using raw IP addresses means no DNS logs, but there are HTTP logs. DNS sinkholes.
    • In a reverse DNS lookup, PTR might contain- 2.152.80.208.in-addr.arpa, which will map to 208.80.152.2. DNS lookups start at the end of the string and work backwards, which is why the IP address is backwards in PTR.
    • DNS configs
      • Start of Authority (SOA).
      • IP addresses (A and AAAA).
      • SMTP mail exchangers (MX).
      • Name servers (NS).
      • Pointers for reverse DNS lookups (PTR).
      • Domain name aliases (CNAME).

  • DNS Exfiltration

    • Sending data as subdomains.
    • 26856485f6476a567567c6576e678.badguy.com
    • Doesn’t show up in http logs.

  • ARP (Address Resolution Protocol)

    • Pair MAC address with IP Address for IP connections.

  • DHCP (Dynamic Host Configuration Protocol)

    • UDP (67 - Server, 68 - Client)
    • Dynamic address allocation (allocated by router).
    • DHCPDISCOVER -> DHCPOFFER -> DHCPREQUEST -> DHCPACK

  • Multiplexing

    • Timeshare, statistical share, just useful to know it exists.

  • Traceroute

    • Usually uses UDP, but might also use ICMP Echo Request or TCP SYN. TTL, or hop-limit.
    • Initial hop-limit is 128 for windows and 64 for *nix. Destination returns ICMP Echo Reply.

  • Nmap (Network Mapper)

    • Network scanning tool.

  • Person‐in‐the‐Middle (PitM)

    • Understand PKI (public key infrastructure in relation to this).

  • VPN (Virtual Private Network)

    • Hide traffic from ISP but expose traffic to VPN provider.

  • Tor (The Onion Router)

  • Proxy

  • BGP (Border Gateway Protocol)

    • Border Gateway Protocol.
    • Holds the internet together.

  • Network Traffic Analysis Tools

    • Wireshark
    • Tcpdump
    • Burp suite

  • HTTP(S)

    • (80, 443)

  • SSL/TLS

    • (443)
    • Super important to learn this, includes learning about handshakes, encryption, signing, certificate authorities, trust systems. A good primer on all these concepts and algorithms is made available by the Dutch cybersecurity center.
    • POODLE, BEAST, CRIME, BREACH, HEARTBLEED.

  • TCP/UDP

    • Web traffic, chat, voip, traceroute.
    • TCP will throttle back if packets are lost but UDP doesn't.
    • Streaming can slow network TCP connections sharing the same network.

  • ICMP

    • Ping and traceroute.

  • Email Protocols

    • SMTP (25, 587, 465)
    • IMAP (143, 993)
    • POP3 (110, 995)

  • SSH

    • (22)
    • Handshake uses asymmetric encryption to exchange symmetric key.

  • Telnet

    • (23, 992)
    • Allows remote communication with hosts.

  • ARP

    • Who is 0.0.0.0? Tell 0.0.0.1.
    • Linking IP address to MAC, Looks at cache first.

  • IRC

    • Understand use by hackers (botnets).

  • FTP/SFTP

    • (21, 22)

  • RPC

    • Predefined set of tasks that remote clients can execute.
    • Used inside orgs.

  • Service Ports

    • 0 - 1023: Reserved for common services - sudo required.
    • 1024 - 49151: Registered ports used for IANA-registered services.
    • 49152 - 65535: Dynamic ports that can be used for anything.

  • HTTP Header

    • | Verb | Path | HTTP version |
    • Domain
    • Accept
    • Accept-language
    • Accept-charset
    • Accept-encoding(compression type)
    • Connection- close or keep-alive
    • Referrer
    • Return address
    • Expected Size?

  • HTTP Response Headers

    • HTTP version
    • Status Codes:
      • 1xx: Informational Response
      • 2xx: Successful
      • 3xx: Redirection
      • 4xx: Client Error
      • 5xx: Server Error
    • Type of data in response
    • Type of encoding
    • Language
    • Charset

  • UDP Header

    • Source port
    • Destination port
    • Length
    • Checksum

  • Broadcast Domain vs Collision Domain

  • Root Store

  • CAM Table Overflow