new computer security

ch1-4

integrity

guarantee that the data is what we expected, not altered

confidentiality

the information must be accessible to the authorized people

reliability

computer should work without having unexpected problems

availability

guarantee that system always available

network attack

• packet sniffing

• man in the middle

• DNS hijacking

web attacks

• phishing

• SQL injection

• cross site scripting

OS, application and software attacks

virus, Torjan, worms,rootkit ,buffer overflow

packet sniffing

Internet traffic is "packets"; an attacker listens. Leads to password sniffing, cookie stealing, session hijacking.

man in the middle

Attacker sits between client and server and changes packets passing through.

insert a router in the path between client and server

DNS hijacking

nsert malicious routs into DNS so a real site's name sends you to a fake site

phishing

Fake site pretending to be trusted

mibank.com vs mybank.com

SQL injection

Attacker's input becomes part of the database query.

Cross-site scripting (XSS)

Malicious JavaScript that steals data from your browsing session.

Virus

Self-copying code attached to a file/program; needs user action to spread

• infection,

• propagation,

• payload

Worm

elf-copying over the network; autonomous.

Parts:

• infection,

• propagation engine,

• target selection,

• scanning engine,

• payload.

Backdoor

Program that lets a hacker back into a system

• keyboard sniffer,

• screen spying

Torjan

Looks useful or harmless but hides malicious function.

Rootkit

Backdoor/Trojan plus modifies OS programs to stay hidden (user-mode or kernel-mode).

Password attacks

• guessing

• dictionary

• rainbow table

Guessing

ineffective except in targeted cases

Dictionary

passwords are stored as hashes;

if hashes leak, try every known word and compare.

Rainbow table

trade storage for speed using a huge set of pre-computed hashes (no dictionary needed).

Slide example: 14-character alphanumeric found in ~4-10 min with a 1 GB table.

vulnerability

point where a system is susceptible to attack

threat

possible danger to the system

countermeasures

techniques for protecting the system

Encryption

data to unreadable code;

you need the key to get it back.

Public keys

prove you know your secret without revealing it; also digital signatures; used in SSL.

Hashing

a "fingerprint" of a document.

Nonrepudiation

Un-forgeable evidence a third party can verify (origin = sender proof; delivery = receipt proof).

Accountability

Users answer for actions: so identify + authenticate users and keep an audit trail.

Privacy

protect personal data

secrecy

protect organization's data

authentication must achieve

• correctness

• impersonation resistance

• transferability resistance

identification factors

• something you know

• something you are

• something you have

password properties

• unilateral

• no third party

• low complexity ?

attacks on fixed passwords

• replay attacks

• exhaustive search

• password guessing

protecting passwords

• salting

• slow down mapping

Password management / SSO

SSO uses an agent on each system. Shared privileged passwords hurt accountability → intermediary issues individual one-time passwords

PIN

short (4 digits), used with a card. Lock the account/confiscate card after 3-4 failures. Two-stage: card holds the high-entropy key.

Passphrase

long sentence; but real words so smaller search space

Passkey

phrase mapped to a pseudo-random key

One-time passwords (OTP)

defeat eavesdropping/replay. Shared list, or sequential update.

Graphical

click points in a picture (points + order).

Anti-shoulder-surfing: pick triangles, reorder icons.

Personal history questions

"which address did you live at?" Used by credit bureaus. Reasonable, not strong; attacker can research you.