2.2 interfacing computers mr joseph tan choo kee tuesday 1330 to 1530
TRANSCRIPT
2.2 Interfacing ComputersMR JOSEPH TAN CHOO KEETUESDAY 1330 TO 1530 http://computing2013.wiki.hci.edu.sg/
Different type of Servers*Servers has dedicated roles
File server is a computer and storage device dedicated to storing files Any user on the network can store files onto the server
Print server is a computer that manages one or more printers
Mail ServersAn e-mail server is a computer within your network that works as your virtual post office. It handles the transfer of messages to and from other mail servers and email clients.
Proxy Serverssit between a client program typically a Web browser and an external server (typically another server on the Web) to filter requests, improve performance, and share connections.
Domain Name ServersDomain Name systems: Allows Clients to query for IP addresses(32 bit) of hostnames.
Mail ServersAn e-mail server is a computer within your network that works as your virtual post office. It handles the transfer of messages to and from other • mail servers and • email clients.
Components• Sender workstation (Sender Client)• SMTP (Simple Mail Transfer Protocol) Server
• Internet Standard for Electronic mail transmission across Internet• It is a protocol to send emails• Text only, extensions are created to expand on it eg. Video, images
• Email messages storage (Receiver Server)• Receiver Workstation (Receiver Client)
How does mail server works?Example [email protected] sends an email to [email protected]
Sender Client
Receiver Client
Client: SMTP Server
Receiver: SMTP Server
Internet
Question:• What happens if its send to the same SMTP server?• What happens if it cannot locate the receiver?
mail.hci.edu.sg
mail.moe.edu.sg
SMTP/POP3
2 main categories of Mail servers: • Outgoing mail servers
• Simple Mail Transfer Protocol• Incoming mail servers
• POP3 (Post Office Protocol, Version 3)• storing sent and received messages on local• Most POP3 servers can store messages on servers, too
Proxy Servers
Sit between a client program typically a Web browser and an external server (typically another server on the Web) to • filter requests (acts as a firewall), • improve performance(Log activity, caching), and
Goal: satisfy client request without involving origin server
http://www.youtube.com/watch?v=qU0PVSJCKcs
Firewalls
Objective is to keep the network secure. • To control the incoming and outgoing network traffic by analyzing the data
and determining whether it should be allowed through or not, based on a predetermined rule set.
• Filter based on data packets/applications
http://www.youtube.com/watch?v=qU0PVSJCKcs
Proxy Servers
Browser sends all HTTP requests to cache (proxy)• If object in cache: cache returns object• Else cache requests object from origin server, then returns object to client
Why caching?• Reduce response time for client request• Reduce traffic
http://www.youtube.com/watch?v=qU0PVSJCKcs
DNS (Domain Name System)
There are 2 ways to identify a host• host names• IP addresses
Routers identify a host by IP addresses. Eg. 121.7.106.83Easier to remember a host by its name. Eg. www.hci.edu.sg
DNS provides the directory service to translation from hostnames to IP addresses.
DNS is a• Distributed database implemented in a hierarchy of DNS servers• It allows hosts to query the database
Cache in Browser + OS
Resolving Name ServerBy ISP or Organization admin
Root Server
Top Level DNS Server,
Authoritative DNS Servers
DNS: Root Name Servers
http://www.youtube.com/watch?v=72snZctFFtA
What are the different type of servers?
Mail Servers• An e-mail server is a computer within your network that works
as your virtual post office. It handles the transfer of messages to and from other mail servers and email clients.
Proxy Servers• sit between a client program typically a Web browser and an
external server to filter requests, improve performance, and share connections.
Domain Name Systems• Using a hierarchy of DNS servers to allows Clients to query for
IP addresses of hostnames.
Mail Servers• An e-mail server is a computer within your network that works as
your virtual post office. It handles the transfer of messages to and from other mail servers and email clients.
• Elaborate on how messages get transferred from 1 domain to another.
Proxy Servers• sit between a client program typically a Web browser and an
external server to filter requests, improve performance, and share connections.
• Elaborate on how it filter requests, improve performance, and share connections.
Domain Name Systems• Using a hierarchy of DNS servers to allows Clients to query for IP
addresses of hostnames.• Elaborate on process of querying the different levels of servers.
Network security
Security: Questions
1. What are the security threads?2. What are some of the possible problems with breach of security?3. What kind of data get ‘stolen’?4. What are the current security measures in place?5. What can the Singapore government do to ensure security measures are in
place?
Case Studies• Breaches• Sony Playstation
• http://www.youtube.com/watch?v=eh0vSIs3wtg
Questions:What are the security threads?What are some of the possible problems with breach of security?What kind of data get ‘stolen’?What are the current security measures in place?
Case Studies• Sony Playstation
Questions:What are the security threads?• Servers get hacked! Servers with customer/player personal data
What kind of data get ‘stolen’?• Personal data stolen, 70 + 25 million, names address and Credit card
numberWhat are some of the possible problems with breach of security?• Data theft, Identity theft and Credit card fraud
What are the current security measures in place????
Data scare
• Citibank• Affects 100,000 North American customers• affecting about 200,000 accounts• Stolen 2.7 Million
• Sony• Multiple attacks, 1 million users compromised• Pull PlayStation gaming networks offline
• Account information being compromised• Name, address, email address, Date of birth• Plaintext password, encrypted password
• Damages• Trust/Reputation• $
Case study: Target http://www.youtube.com/watch?v=E_F8z1g0nbE
1. What are the security threads?• Using Malware to infect computer systems• The Malware is scripted/embedded into another software
2. What kind of data get ‘stolen’?• Personal information(Card/pin numbers), Address
3. What are some of the possible problems with breach of security?• Data theft, Identity theft and Credit card fraud
4. What are the current security measures in place?• Awareness
Malware
What?software used to • disrupt computer operation, • gather sensitive information, or • gain access to private computer systems.
Questions to discuss
Give 3 real life cases of security breaches/copy right issues etc in Singapore. Briefly describe how they have impacted the society and the organization involved.
Recently, end of 2013• Hackers threatens to hit out on Singapore’s infrastructure• Hackers compromise government websites• Hackers defaced school web sites
Threats posted on youtube
Video: http://www.youtube.com/watch?v=CwEyB42swMU
Case 1: School website Defaced
13 school website gets defaced• http://
www.channelnewsasia.com/news/singapore/websites-of-13-schools/893806.html
Case 2: 17 website related to People’s Association hacked
News: • http://www.youtube.com/watch?v=VYNIwKvLo9I
Case 2: PMO and Isetana Website compromised
• News • http://www.youtube.com/watch?v=uu0QLFWicNk• Using cross-scripting => pointing to another page
• 2 men arrested for hacking into the websites• http://www.youtube.com/watch?v=_4ImQnxPBy4
Case 2: PMO and Isetana Website compromised
• News video: http://www.youtube.com/watch?v=uu0QLFWicNk• Using cross-scripting => pointing to another page
• 2 men arrested for hacking into the websites• http://www.youtube.com/watch?v=_4ImQnxPBy4
Punishments• Charged in court under Computer Misuse & Cyber Security Act • Fine: $10 000 • Jail up to 3 years
Case 3: Singapore Art Museum website compromised
• Nov 20 & Nov 29• News:• http://
www.straitstimes.com/breaking-news/singapore/story/sam-website-hacked-second-cyber-intrusion-within-month-20131129
• Internal investigations found that unauthorised links had been added to a specific page of the website.
• On Nov 20, personal information of about 4,000 people on its online mailing list was compromised
• Video: http://www.youtube.com/watch?v=ZkXKGFyIERc
Examples• Posting threads to Singapore government on the Internet• Govt to reconsider its regulation for licensing of news site
• Defaced school websites: Intention unclear• Hacked Government websites• People’s associations: intentions unclear• PMO & Isetana: Intentions unclear• Singapore Art Museum: Data theft
Government’s Take• Video: http://www.youtube.com/watch?v=eACG7tIRoOc• What is the Computer Misuse Act?
(SG)Computer Security Act
Offences:
1. Unauthorised access to computer material2. Access with intent to commit or facilitate commission of offence3. Unauthorised modification of computer material4. Unauthorised use or interception of computer service5. Unauthorised obstruction of use of computer6. Unauthorised disclosure of access code7. Enhanced punishment for offences involving protected computers8. Abetments and attempts punishable as offences
(SG)Computer Security Act
Offences:
Unauthorised access to computer material• any person who knowingly causes a computer to perform any
function for the purpose of securing access without authority to any program or data held in any computer shall be guilty of an offence and shall be liable on conviction to a fine
(SG)Computer Security Act
Offences:
Access with intent to commit or facilitate commission of offence• Any person who causes a computer to perform any function for
the purpose of securing access to any program or data held in any computer with intent to commit an offence to which this section applies shall be guilty of an offence
(SG)Computer Security Act
Offences:Unauthorised modification of computer material• any person who does any act which he knows will cause an
unauthorised modification of the contents of any computer shall be guilty of an offence and shall be liable on conviction to a fine
(SG)Computer Security ActOffences:
Unauthorised use or interception of computer serviceAny person who knowingly —(a)secures access without authority to any computer for the purpose of obtaining, directly or indirectly, any computer service;(b) intercepts or causes to be intercepted without authority, directly or indirectly, any function of a computer by means of an electro-magnetic, acoustic, mechanical or other device; or(c) uses or causes to be used, directly or indirectly, the computer or any other device for the purpose of committing an offence under paragraph (a) or (b),
shall be guilty of an offence and shall be liable on conviction to a fine
(SG)Computer Security Act
Offences:Unauthorised obstruction of use of computer
Any person who, knowingly and without authority or lawful excuse —(a) interferes with, or interrupts or obstructs the lawful use of, a computer; or(b) impedes or prevents access to, or impairs the usefulness or effectiveness of, any program or data stored in a computer,shall be guilty of an offence and shall be liable on conviction to a fine
(SG)Computer Security Act
Offences:Unauthorised disclosure of access code• Any person who, knowingly and without authority, discloses any
password, access code or any other means of gaining access to any program or data held in any computer shall be guilty of an offence
(SG)Computer Security ActOffences:Enhanced punishment for offences involving protected computers
a computer shall be treated as a “protected computer” if the person committing the offence knew, or ought reasonably to have known, that the computer or program or data is used directly in connection with or necessary for —(a)the security, defence or international relations of Singapore;(b)the existence or identity of a confidential source of information relating to the enforcement of a criminal law;(c)the provision of services directly related to communications infrastructure, banking and financial services, public utilities, public transportation or public key infrastructure; or(d)the protection of public safety including systems related to essential emergency services such as police, civil defence and medical services.
(SG)Computer Security Act
Offences:
Abetments and attempts punishable as offences• Any person who abets the commission of or who attempts to
commit or does any act preparatory to or in furtherance of the commission of any offence under this Act shall be guilty of that offence and shall be liable on conviction to the punishment provided for the offence.
Security: Questions
1. What are the security threads?2. What are some of the possible problems with breach of security?3. What kind of data get ‘stolen’?4. What are the current security measures in place?5. What can the Singapore government do to ensure security measures are in
place?