Security+

Introduction

This will only include very brief notes from my studies leading up to taking the CompTia Security+ exam.

Risk Assessments

• Quantitative Risk Assessment
  • Asset Value (AV) -- what is the worth of the asset
  • Exposure Factor (EF) -- how much of the asset do we lose for a specific exposure
  • Single Loss Expectancy (SLE)
    • includes hard numbers to backup your assessment
    • Multiply the AV * EF
    • EF = 10%; AV = 25K; SLE = 0.1 * 25,000 = $2,500
    • 24hrs in a day. One day of business is worth $1M. An outage of 3 hours has an Exposure Factor = 3/24 = 12.5%
      • $1M * 12.5% = $125,000 for a single loss expectancy
  • Annual Rate of Occurrence (ARO)
    • Number of times you expect an SLE might occur in a year
      • ARO of 2 times per year = $125k SLE * 2 = $250K. So, we have up to $250K to spend on ways to thwart this risk.
• Qualitative Risk Assessment
  • can be subjective and without many hard numbers
  • Likelihood of it happening
  • Impact if it happens
  • Risk Register -- maintain a list of all the risks and the controls to mitigate the risk

    RiskNo	Title	Likelihood	Impact	Severity	Owner	Mitigation
    1	Some Title	High, Med, Low	High, Med, Low	High, Med, Low	Dept1	Mit 1
    2	Some Title 2	High, Med, Low	High, Med, Low	High, Med, Low	Dept2	Mit 2
    3	Some Title 3	High, Med, Low	High, Med, Low	High, Med, Low	Dept3	Mit 3

  • Risk heat map
    • 
      • The numbers in parenthesis represent the risk level after mitigation

Linux Commands

• fdisk -l
• sudo
• mkfs -t ext4 /dev/devname
• mount /dev/devname /folder
• touch
• dd if=/dev/urandom of=/dev/devname # wipe a drive
• umount
• ssh-keygen
• ssh-copy-id -i filename.pub uid@hostname.domain.com
• cat

Cryptography

• obfuscation
• rot13
• integrity
• hash
  • MD5 - 128 bit hash
  • SHA - SHA-1 - SHA-2
  • RIPEMD - 128 160
  • Attack the algorhythm, attack the implementation, attack the key

Password Cracking

• Rainbow tables
• salting
• brute force
• unshadow /etc/passwd /etc/shadow > credentials.txt # jack the ripper