Computer & Data Security
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Here are some ways I would optimize the backup strategy: - Only back up data directories instead of entire hard disks to reduce backup size and time. - Stagger backups throughout the night instead of all at once to avoid overloading the network. - Store backups offsite as well as on the NAS for disaster recovery in case the onsite storage is damaged. - Consider cloud backup services for additional offsite storage. - Encrypt backups for security and confidentiality. - Test restores periodically to validate backups are working properly. - Consider versioning backups to allow restoration of previous file versions. - Automate verification of backups to catch any failures or corrupt backups. - Review
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Computer & Data Security
- 1. Computer & Data Security Prof. dr. Frederik Questier - Vrije Universiteit Brussel Presented at: Arba Minch University, Ethiopia, 03/2019
- 3. Main objectives of computer security ➢ Confidentiality ➢ of data (secrecy) ➢ of persons (privacy) ➢ access only by authorized parties ➢ Integrity ➢ data only correctly modified or deleted by authorized parties ➢ Availability ➢ correctly accessible in a timely manner ➢ the failure to meet this goal is called a denial of service
- 4. Assignment Risk analysis Congratulations! You are elected member of the newly established computer and data security team in the university. Make a list of all possible risks that can have an impact on the security and stability of your internal and external IT services.
- 5. What can go wrong? Nature ➢ lightning strike ➢ fire ➢ flood ➢ heat wave – cold wave ➢ storm weather, hurricane ➢ earthquake ➢ tsunami ➢ volcano eruption ➢ electro magnetic pulse from the sun ➢ disease of key employees
- 6. What can go wrong? Infrastructure or services problems ➢ Failure of ➢ software (bugs; license expired, ...) ➢ hardware ➢ electricity ➢ power outage or power surge ➢ network (cable cut – saturation) ➢ airconditioning ➢ water pipes –> leak ➢ system upgrades ➢ service providers (e.g. cloud) ➢ Overload of CPU, memory, storage, network (spam)
- 7. What can go wrong? Human errors ➢ Weak security ➢ Loss of laptops, smartphones, USB-sticks, … ➢ No encryption ➢ Passwords leaks or cracks ➢ Computer console left unlocked ➢ Misunderstanding computer interface or other mistakes ➢ Deleting data ➢ Corrupting data ➢ Confiscation of machines
- 8. What can go wrong? Evil actions by people ➢ break in (hackers - crackers) ➢ social engineering ➢ phishing ➢ (identity) theft ➢ vandalism ➢ unhappy employees ➢ sabotage (time bomb), leaks ➢ cyber attack, e.g. (Distributed) Denial of Service ➢ terrorism ➢ war ➢ nuclear bomb
- 9. What can go wrong? Malware (malicious software) ➢ Botnet ➢ Rootkit ➢ Back door ➢ Spyware ➢ keylogger ➢ network sniffer ➢ Dialer ➢ Ransomware
- 10. Business continuity planning = how to stay in business in the event of disaster? ➢ Disaster recovery ● Preventive measures ● Detective measures ● Corrective measures
- 11. Threat modeling 1) What do you want to protect? 2) Who/what do you want to protect it from? 3) How likely is it that you will need to protect it? 4) How bad are the consequences if you fail? 5) How much trouble are you willing to go through in order to try to prevent those?
- 12. Tools for computer security
- 13. Tools for confidentiality ➢ Authorization - access policies - access control ➢ Authentication – identification ➢ Passwords ➢ … ➢ Encryption ➢ Virtual private networking ➢ Auditing – logging ➢ ...
- 15. Tools for availability ➢ Disaster recovery planning ➢ Physical protections ➢ Anti-theft ➢ Uninterruptible Power Supply ➢ Redundancies ➢ Intrusion-detection systems ➢ Antivirus software ➢ Firewall ➢ ...
- 17. Passwords ➢ Don't share them ➢ Not even with computer administrators ➢ Don't write them down ➢ Don't reuse them among different sites ➢ Change them often ➢ Select wise: ➢ Easy to remember ➢ Hard to guess (resistant to dictionary attacks) ➢ Password length ➢ Large set of characters (caps, lower case, numbers, symbols)
- 18. Some notorious password leaks ➢ 2016: 500M Yahoo passwords ➢ 2015: 30M Ashley Madison MD5 passwords etc ➢ 2014: 5M Gmail passwords ➢ 2013: 38M Adobe passwords (and source code) ➢ 2013: 250K Twitter passwords ➢ 2012: 12M Apple User IDs stolen by FBI, 1M leaked ➢ 2012: 6M LinkedIn passwords ➢ 2012: 450K plain text Yahoo passwords ➢ 2012: 1.5M plain text Youporn passwords ➢ 2009: 10K MS Hotmail, MSN and Live passwords
- 21. Passphrases are more secure than passwords
- 23. Biometric identification ➢ Finger print ➢ Voice print ➢ Iris scan ➢ Retinal scan ➢ Convenient ➢ Relative safe ➢ But...
- 25. Danger of biometric identification? ➢ You can't change your biometric password once it got leaked ➢ You can't legally refuse to give it, unlike a password (US fifth amendment) ➢ Something like a fingerprint might be unusable as a password, because you leave copies of your fingerprints on everything you touch. ➢ Fingerprint is more like a login than like a password.
- 26. Lock your screen when you leave
- 27. Security issues in communication PrivacyPrivacy IntegrityIntegrity AuthenticationAuthentication Non-repudiationNon-repudiation Interception Spoofing Modification Proof of parties involved
- 29. Cryptography = secret writing
- 31. Cipher algorithm for performing encryption or decryption ➢ Example: Caesar cipher
- 36. Great if we can exchange our messages encrypted! But how can we safely exchange our keys?
- 37. Symmetric encryption Sender and receiver must both know the same secret key How to exchange that key over distance??? Asymmetric encryption Sender only needs to know the public key of receiver!
- 38. Public key encryption The private key can unlock (decrypt) what is locked (encrypted) with the public key
- 39. Public key encryption Creation of keys
- 44. Man-in-the-middle attack ➢ How can Bob know that Alice's key is really Alice's key (and not Mallory's)?
- 45. Digital certificates Version # Serial # Signature Algorithm Issuer Name Validity Period Subject Name Subject Public Key Issuer Unique ID Subject Unique ID Extensions Digital Signature
- 47. ➢ CAcert.org is a community-driven certificate authority that issues free public key certificates to the public (unlike other certificate authorities which are commercial and sell certificates). ➢ CAcert has over 200,000 verified users. ➢ These certificates can be used to digitally sign and encrypt email, authenticate and authorize users connecting to websites and secure data transmission over the Internet.
- 48. Web of trust Keysigning parties
- 49. Belgian eID contains personal authentication certificate signature certificate Two factor auth: possession of eID and knowledge of pin code
- 50. Private keys never leave eID! Signatures are computed in eID on hash of file-to-be-signed (SHA-1 = Secure Hash Algorithm)
- 51. Error detection - Checksum - cryptographic hash e.g. CRC32 (cyclic redundancy check) MD5 (message digest) SHA-3 (Secure Hash Algorithm)
- 52. Belgian electronic medical prescriptions are based on the e-ID ➢ Doctor is identified with e-ID ➢ Patient is identified with e-ID ➢ Doctor signs the prescription with e-ID ➢ Prescription is stored in national Recip-e database. ➢ Patient can consult prescriptions in patient portal with e-ID ➢ Pharmacist is identified with e-ID ➢ Pharmacist finds the prescription in the Recip-e database with barcode on the paper version of the prescription.
- 53. ➢ Encrypted protocols ➢ HTTPS ➢ SFTP ➢ SSH ➢ TOR ➢ VPN ➢ WEP (Wired Equivalent Protocol. Weak!) ➢ WPA - WPA2 Wi-Fi Protected Access ➢ Non-encrypted protocols ➢ HTTP ➢ FTP ➢ TELNET ➢ BitTorrent
- 54. Telegram and Signal ➢ Free Open Source software ➢ End to end encryption ➢ Delete messages everywhere ➢ Self-destruct timer for messages ➢ VOIP ➢ User friendly ➢ For Android, iOS, …
- 60. Virtual drive in file container Encrypted file container.txt Mountable as virtual drive /media/encrypted-disk /Volumes/encrypted-disk E:
- 65. Virtual Private Networks extends a private (hospital) network across a public (internet) network encrypted to protect against network sniffing
- 66. Internet use through a VPN provider Sarah A. Downey, http://www.abine.com/blog/2012/petraeuss-emails-werent-private-and-neither-are-yours/
- 67. (Free) VPNs? ➢ VPNs good for ➢ protection against nearby spying and MITM attack ➢ avoiding geoblocking ➢ But you need to trust your VPN provider ➢ The free VPNs might have a business model based on spying on you. ➢ Don’t install their proprietary apps ➢ The good VPN providers support OpenVPN ➢ Best to install e.g. OpenVPN on your own server.
- 70. Private browsing
- 72. = The Onion Router Free Open Source software for anonymity network
- 73. Edward Snowden: “Encryption works. Properly implemented strong crypto systems are one of the few things that you can rely on. Unfortunately, endpoint security is so terrifically weak that NSA can frequently find ways around it.”
- 75. ➢ From the European Parliament investigation into the Echelon system (05/18/2001): “If security is to be taken seriously, only those operating systems should be used whose source code has been published and checked, since only then can it be determined with certainty what happens to the data.”
- 76. ➢ Cryptographer, computer security expert Bruce Schneier: “Secrecy and security aren't the same, even though it may seem that way. Only bad security relies on secrecy; good security works even if all the details of it are public." “If researchers don’t go public, things don’t get fixed. Companies don't see it as a security problem; they see it as a PR problem.” “Demand open source code for anything related to security”
- 77. The Borland Interbase example ➢ 1992-1994: Borland inserted intentional back door into Interbase (closed source database server) allowing local or remote users root access to the machine ➢ 07/2000: Borland releases source code (→ Firebird) ➢ 12/2000: Back door is discovered
- 78. Your opinion?
- 81. “Our products just aren’t engineered for security.” Brian Valentine, Microsoft senior vice-president Windows Engineering, 2002
- 84. Be aware of phishing attacks
- 86. Backups How would you optimize this backup strategy? ➢ Every night at 4 am, all university computers get a wake up signal. ➢ The backup server takes over network a complete backup of every hard disk of every computer. ➢ The backups are stored on a NAS (Network Attached Storage) with 1000 hard disks. ➢ The backup server and the NAS are located in the data center of the university (floor level -1). ➢ To save storage space, backups older than a year are deleted.
- 87. Backup Example: centralized over network
- 88. Backups ➢ First time and sometimes: full backup ➢ Most often: only incremental backup ➢ Use a good data retention scheme ➢ e.g. 7 daily, 4 weekly, 12 monthly, all yearly backups ➢ + Use off-site data protection = vaulting ➢ e.g. remote backup (compression, encryption!) ➢ Use offline backups as protection against ransomware ➢ Reflect about your time for full restore ➢ Test the restore procedure! ➢ “80% of backups fail to restore”
- 90. (Cheap) versioning For important documents save daily new version as: thesis20190307.odt This avoids overwriting backups with corrupt data See also https://en.wikipedia.org/wiki/ISO_8601
- 93. Uninterruptible Power Supply UPS 1)Flywheel 2)Diesel generators 3)Batteries (UPS)
- 94. Your toilets are better locked than your electrical switches
- 95. DDoS Distributed Denial of Service
- 98. RAID: Redundant Array of Independent Disks
- 101. Install software from trusted sources! (avoid if possible P2P or web downloads)
- 102. Apply software updates and upgrades!
- 103. If you don’t apply security fixes fast enough... ➢ Microsoft ➢ Patch Tuesday ➢ Exploit Wednesday
- 104. Principle of least privilege Avoid privilege escalation
- 105. Intrusion Detection Systems (IDS) ➢ Fail2ban ➢ Snort ➢ real-time traffic analysis and packet logging ➢ detect probes or attacks ➢ Samhain ➢ Complete integrity check ➢ uses cryptographic checksums of files to detect modifications, ➢ can find rogue SUID executables anywhere on disk ➢ Centralized monitoring ➢ native support for logging to a central server via encrypted and authenticated connections ➢ Tamper resistance ➢ database and configuration files can be signed ➢ log file entries and e-mail reports are signed ➢ support for stealth operation ➢ Honey pots ➢ ...
- 106. Subscribe to security mailing lists of the critical software you are using
- 107. Assignments ➢ Make a risk analysis and threat modeling of the computer and data systems at your organization. What are the weakest and most unsecure parts? ➢ Risk ... probability * potential impact = total risk level ➢ Which actions will you take to increase the security at your organization? ➢ Why are some operating systems more secure than others? ➢ Compare the security characteristics of the Linux operating system and Windows
- 108. Windows versus Linux security ➢ Windows origin ➢ QDOS (Quick and Dirty Operating System, 1980) ➢ To fit in small 8086 Personal Computer all existing concepts of security, network, multi-user, … where omitted. ➢ 86-DOS ➢ MSDOS ➢ Windows ➢ Linux (1991) ➢ Modeled according to UNIX, with security, network and multi-user concepts implemented from the beginning.
- 109. Windows versus Linux security ➢ Windows and its software ➢ Source code mostly secret ➢ Cannot be audited ➢ Microsoft’s self-inflicted curse of binary compatibility: ➢ Major design improvements are hard as Microsoft cannot modify & recompile proprietary software by others ➢ Linux and its software ➢ Free Open Source ➢ Source code can be audited, bugs and backdoors found ➢ Major design improvements are easier to implement
- 110. Windows versus Linux security ➢ Windows software ➢ Often (illegal copies) downloaded from web or P2P ➢ No checksum or signature ➢ Often malware. No way to detect it. ➢ Installer = executable ➢ Any malware gets executed with admin privileges ➢ Linux ➢ Software is installed through package manager ➢ Package maintainers of the many distributions often audit code and compile from source. ➢ Package maintainers sign the packages and provide checksums ➢ Package = compressed archive only unpacked by root
- 111. Windows versus Linux security Updates ➢ Windows update manager is only updating Windows (and other Microsoft software?) ➢ Linux update manager is updating all software installed through the package manager, which is typically near 100%.
- 112. Windows versus Linux security User attitudes towards updates & upgrades ➢ Windows users don’t like updates & upgrades ➢ Windows reboots for updates ➢ System cannot be used during installation of the updates ➢ Users have very little control over updates ➢ Updates often come with more anti-user features ➢ Microsoft forces GUI changes upon upgrades ➢ Users continue with outdated OS when they don’t like GUI of newer version ➢ Linux ➢ Software and kernel(!) updates can be installed without rebooting or unavailability of the system ➢ Users have total control over updates ➢ User can select the GUI indepentdently from upgrades
- 113. Windows versus Linux security Who gets updates ➢ Windows and its software ➢ Sometimes “pirate users” did not get updates ➢ Linux and its software ➢ Users are never labeled as “pirates” ➢ Users are not denied updates
- 114. Windows versus Linux security ➢ Windows ➢ Not modular ➢ Most versions can’t be run without GUI ➢ No strict separation between kernel and GUI, webbrowser, games, … ➢ Any bug in these can lead to crash or intrusion of the kernel ➢ Linux and its software ➢ Modular ➢ GUI is an option ➢ Strict separation between kernel and user space
- 115. Windows versus Linux security ➢ Windows ➢ Decides if a file is executable based on extension ➢ Read and execute permissions are not distinct ➢ “50+ File Extensions that are Potentially Dangerous on Windows” ➢ Windows hides extensions by default, but only the last one ➢ file.jpg.exe is visible as file.jpg ➢ Mail attachments can infect you with malware ➢ Linux ➢ Decides if a file is executable based on execution bit ➢ Read and execute permissions are distinct ➢ Nobody was stupid enough to write a Linux mail client that sets the execution permission on attachments.
- 116. Windows versus Linux security ➢ Windows ➢ Autorun software from CD and USB (until Windows 7) ➢ Linux ➢ Autorun is not default or asks user permission
- 117. Windows versus Linux security ➢ Windows ➢ Many users work day in day out with an admin account ➢ Linux ➢ Users get a big fat warning when they attempt to login in the GUI as root ➢ Users get very low privileges ➢ Different crucial applications run on different user accounts ➢ E.g. Apache web server runs as user www ➢ User www has only (write) access to its own files.
- 118. Windows versus Linux security ➢ Windows ➢ FAT and NTFS still don’t have the option to create a non- executable partition? ➢ Linux ➢ /tmp can be set as noexec ➢ This prevents that malware uploaded through e.g. webserver can be executed.
- 119. Windows versus Linux security ➢ Windows ➢ Monoculture ➢ Linux ➢ 300+ distributions ➢ 84+ window managers ➢ Many packaging systems ➢ Many mail clients ➢ The diversity slows down widespread malware infections as these will not work for all Linux systems.
- 120. Windows versus Linux security ➢ Windows filesystems ➢ Not much more than FAT and NTFS ➢ Linux ➢ Supports tens of filesystems ➢ Including some high availability oriented ones such as ZFS.
- 121. Windows versus Linux security Matheus effect ➢ Windows ➢ Many users don’t care about security ➢ Linux ➢ Users caring about security will rather use Linux ➢ These users secure their systems more ➢ Linux get more attention by security caring developers
- 122. Credits ➢ Password Strength, Creative Commons BY-NC http://xkcd.com/936/ ➢ Security, Creative Commons BY-NC http://xkcd.com/538/ ➢ Zimmermann Telegram, 1917, no known copyright restrictions ➢ Assymetric and symmetric encryption by Jeremy Stretch, http://packetlife.net/blog/2010/nov/23/symmetric-asymmetric-encryption-hashing/ ➢ Orange blue public key cryptography, Creative Commons CC0 by Bananenfalter ➢ HTTPS SSL Exchange by Robb Perry, http://coding.smashingmagazine.com/2012/05/17/backpack-algorithms-and-public-key-cryptography-made-easy/ ➢ Bitcoin logo, Public Domain by bitboy ➢ Bitcoin Transaction Visual, Creative Commons CC0 by Graingert ➢ Question mark CC-by by Stefan Baudy ➢ GNU Head Joseph W. Reiss Free Art License or the GNU GPLv2
- 123. This presentation was made with 100% Free Software No animals were harmed Questier.com Frederik AT Questier.com www.linkedin.com/in/fquestie www.diigo.com/user/frederikquestier www.slideshare.net/Frederik_Questier T hank you! Q uestions?