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11 Feb 2014Computer networks1 Network administrators are here to help you! Open a ticket on

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1 11 Feb 2014Computer networks1 Network administrators are here to help you! Open a ticket on

2 11 Feb 2014Computer networks2 What is a network Computers External connection Terminals Printers Stand-alone hard disks VoIP telephones Server-client architecture

3 11 Feb 2014Computer networks3 Transfer speed Network areas Local Area Network (LAN, Intranet) Wide Area Network (WAN, Internet) Virtual Private Network (VPN) Speed in bits per second (bps) Ethernet 10 Mbps Fast Ethernet 100 Mbps Giga Ethernet 1 Gbps Wireless 30-300 Mbps

4 11 Feb 2014Computer networks4 Communication programs Web browser Chrome (55% of the market) Mozilla Firefox (25% of the market) Internet Explorer (10% of the market) Safari Mail reader Outlook, Mozilla Thunderbird Webmail and Microsoft Outlook Web App Voice over IP Costs

5 11 Feb 2014Computer networks5 Posta Elettronica Certificata – PEC Standard email No guarantee of senders e-mail address identity No guarantee of senders identity No guarantee that content has not been altered No sent proof No dispatched proof No read proof PEC to PEC: like a raccomandata con ricevuta di ritorno Sent proof Dispatched proof (in practice also) senders address identity and unaltered content

6 11 Feb 2014Computer networks6 Posta Elettronica Certificata – PEC PEC to standard email: like a raccomandata semplice Sent proof Standard email to PEC: like a normal letter Sent and dispatched proves are legal proves Every citizen may have a free PEC address to communicate with public administration

7 11 Feb 2014Computer networks7 Search engines Crawler technique (8 billions web pages!) Google scoring system Search tricks: Use many keywords Quotations Advanced search Search for images

8 11 Feb 2014Computer networks8 Slow connections NamesEquipment Effective speed Notes PSTN analogical dial-up telephone line and modem 56 Kbps Telephone is busy during connection ISDN ISDN telephone line and modem 128 Kbps Telephone is busy during full speed connection GPRSGSM mobile phone100 Kbps

9 11 Feb 2014Computer networks9 Broadband connections NameEquipmentEffective speedNotes ADSL telephone line and modem 500 Kbps in upload 8-20 Mbps download Congestion Internet cable some Gbps UMTS 3G UMTS mobile phone 7 Mbps Speed depends strongly on environment Wireless Wi-Fi wireless card30-300 Mbps Speed depends on wireless generation WiMax antenna in line of sight and modem 40 Mbps Speed depends strongly on distance

10 11 Feb 2014Computer networks10 Broadband connections ADSL Congestion minimum band guaranteed contract Digital divide 5,400,000 Italians not covered by broadband WiMax 10 Kilometers range line of sight problem

11 11 Feb 2014Computer networks11 Privacy Law 196/2003 on privacy authentication permission training firewall and antivirus 6-12 months update backup every week sensitive data encryption restore within 7 days

12 11 Feb 2014Computer networks12 Encryption Scrambling technique to make text unreadable Public key for encrypting Private key for decrypting 128 bits to be sure

13 11 Feb 2014Computer networks13 Encryption for information exchange G#4hg ! decrypt encrypt f@çd*s È^£(iw, decrypt message 1 message 2 message 3 message 1 message 2 message 3 message 1 message 2 message 3 G#4hg! encrypt f@çd*s È^£(iw, decrypt Trb:-ò°§ Dr4^\|ò9 %$&/òL decrypt

14 11 Feb 2014Computer networks14 Encryption for data storage encrypt decrypt secret data D(£ò§* +]dH secret data encrypt decrypt secret data D(£ò§* +]dH %£)(84 jhgds?ì

15 11 Feb 2014Computer networks15 Digital signature Law 82/2005 Private key for encrypting Public key for decrypting Keys given by certification authorities Combination with PEC Keys expiration Temporal mark

16 11 Feb 2014Computer networks16 Digital signature document encrypt decrypt document document document G#4$h &à?-2y false document encrypt decrypt 2?=zx:-ki 2?=zx:-ki Y&:ò[ fgj?^d

17 11 Feb 2014Computer networks17 Comparison with handwritten signature Digital signatureHandwritten signature Who can sign Needs keys from certification authority and proper tools Everybody instantly Who can verifyEverybody (with proper tools)Handwriting analysts Verification reliability Sure for some years Subjective in dubious cases, no time limit Temporal duration Some years (can be renewed) Until other reliable signatures are available Mass signatures Some seconds for all documents (with proper tools) Some seconds per document Date reliabilityObjective if temporal mark Based on other subjective elements (papers and inks age)

18 11 Feb 2014Computer networks18 Passwords

19 11 Feb 2014Computer networks19 Passwords What can be done with your password? Steal personal data Steal other peoples data Steal money Delete and modify data Steal identity Start illegal activities A standard computer can try 1 million passwords per second

20 11 Feb 2014Computer networks20 Passwords Law 196/2003 Avoid personal data in the password Change password every 3 months Minimum 8 characters Better also: Mix letters, strange characters and numbers Do not use words Use different passwords for different purposes Beware of passwords stored in programs What to do in case of employees absence Alternative password devices smartcard, token key, OTP with display, OTP USB, phone

21 11 Feb 2014Computer networks21 Viruses What does a virus do? Infect Survive Duplicate Damage Virus infection symptoms computer is slow to start unwanted and annoying pop-ups many system errors

22 11 Feb 2014Computer networks22 Viruses Users responsible behaviors downloaded files and email attachments CD, DVD, USB pendrives strange websites updated programs updated antivirus Anti-viruses Checking the whole hard disk Checking suspect files Always running

23 11 Feb 2014Computer networks23 Types of viruses Trojan horse looks like a good program Key logger records your keyboard activity (to get passwords) Back door opens a port on your computer (to let external users in) Adware displays advertisement Spyware spies your activity (to get passwords or for spam targeting) Dialer dials expensive numbers using your PSTN modem

24 11 Feb 2014Computer networks24 Spam unsolicited unwanted bulk email Advertisement: gambling, pornographic websites, medicines, risky investments, software… Chain letters Frauds Phishing Sender is always counterfeited Do not click on links! Do not answer!!! Where do they get my email address? Antispam and blacklists

25 11 Feb 2014Computer networks25 Phishing

26 11 Feb 2014Computer networks26 Phishing example 2,000,000 emails sent 5% arrive to existing users: 100,000 5% of users read the email: 5,000 2% of readers believe in the email: 100 $1,200 from each user Gain: $120,000 In 2005 Mr. David Levi gained $360,000 from 160 people using Phishing on eBay website

27 11 Feb 2014Computer networks27 Safe navigating Navigation security Phishing Viruses Download Save Antivirus Open Avoid visiting and downloading from untrustworthy websites Keep Explorer and Windows up-to-date Intercept your data Secure connection SSL: httpS

28 11 Feb 2014Computer networks28 Attacks from outside Denial of Service zombie computers Firewall which internal program which external address what amount of traffic which kind of data Windows Seven Firewall

29 11 Feb 2014Computer networks29 Backup Why backup? Source: The Cost of Lost Data. The importance of investing in that ounce of prevention by David M. Smith

30 11 Feb 2014Computer networks30 Backup What to backup? Your data files Emails and addresses; browsers configuration Program configuration files Difficult-to-find stuff Where to backup? another hard disk online backup systems: Dropbox, Mozy, Sugarsync rewritable CD and DVD RAID techniques

31 11 Feb 2014Computer networks31 RAID – Redundant Array of Independent Disks JBOD – Just a Bunch Of Disks 2 disks RAID 0 2 disks, fast RAID 1 2 disks but space as for 1, safe vs crash, 24h service Most common solution RAID 10 4 disks but space as for 2, fast, safe vs crash, 24h service None of these techniques is safe versus viruses or human errors!

32 11 Feb 2014Computer networks32 JBOD

33 11 Feb 2014Computer networks33 RAID 1

34 11 Feb 2014Computer networks34 RAID 0

35 11 Feb 2014Computer networks35 RAID 10

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