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

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

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