Scanning

# Scanning - 1 1 Computer Security Basic Networking Concepts...

This preview shows pages 1–3. Sign up to view the full content.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1 1 Computer Security Basic Networking Concepts and Network Hacking Original slides prepared by K. Liszka, Original slides prepared by K. Liszka, The University of Akron The University of Akron for 3460:453/553 for 3460:453/553 2 Binary Numbering System • Uses the number 2 as its base • Binary digits (bits): 0 and 1 • Byte – Group of 8 bits – Can represent 2 8 = 256 different values UNIX and Linux Permissions • UNIX and Linux File permissions are represented with bits – 0 means removing the permission – 1 means granting the permission – 111 (rwx) means all permissions apply 3 Determining Binary Values • Each position represents a power of 2 value – Usually the bit on the right is the least significant bit • Converting 1011 to decimal – 1 x 2 = 1 – 1 x 2 1 = 2 – 0 x 2 2 = 0 – 1 x 2 3 = 8 • 1 + 2 + 8 = 11 (decimal value) 3 2 1 0 4 Understanding Nibbles • Half a byte or four bits • Helps with reading the number by separating the byte – 1111 1010 • Components – High-order nibble (left side) – Low-order nibble (right side) • Converting 1010 1010 to decimal – Low-order nibble • 1010 = 10 (base 10) – Multiply high-order nibble by 16 • 1010 = 10 x 16 = 160 (base 10) – 160 + 10 = 170 (base 10) 5 Octal Numbering System • Uses 8 as its base. – Supports digits from 0 to 7 • Octal digits can be represented with ______ bits. • Permissions on UNIX – Owner permissions (rwx) – Group permissions (rwx) – Other permissions (rwx) • Example: 111 101 001 – Octal representation 751 three 6 Hexadecimal Numbering System • Uses 16 as its base – Support numbers from 0 to 15 • Hex number consists of two characters – Each character represents a nibble – Value contains alphabetic letters (A … F) • A representing 10 and F representing 15 • Sometimes expressed with “0x” in front. 2 7 What’s an IP address (really)? • 32-bit decimal number normally written as four numbers between 1 and 255. – 8 bits / 1 byte / 1 octet • Separated by dots. – dotted-decimal notation 8 ping • A computer network tool used to test whether a particular host is reachable across an IP network. • Sends ICMP “echo request packets” to the target host. • Listens for ICMP “echo response” replies. ping pong 9 Fancier Tools • SuperScan – www.foundstone.com • NetScanTools Pro – Windows: www.netscantools.com – UNIX: www.fping.com 10 Classy IP addresses 240.0.0.0 – 255.255.255.255 E 224.0.0.0 – 239.255.255.255 D 192.0.0.0 – 223.255.255.255 C 128.0.0.0 – 191.255.255.255 B 0.0.0.0 – 126.255.255.255 A Range Class 11 Class A addresses XXX .XXX.XXX.XXX network ID (8 bits) host ID (24 bits) reserved for large corporations and governments reserved for large corporations and governments 12 Class B addresses XXX . XXX .XXX.XXX network ID (16 bits) host ID (16 bits) assigned to large corporations and Internet Service Providers assigned to large corporations and Internet Service Providers 3...
View Full Document

## This note was uploaded on 02/21/2011 for the course CS 567 taught by Professor Dr.shambooupadhyay during the Fall '09 term at SUNY Buffalo.

### Page1 / 12

Scanning - 1 1 Computer Security Basic Networking Concepts...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online