Skype's Robust Security

Disclosure: AB9IL.net is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program such that this site earns advertising fees by linking to Amazon.com. If you make a qualifying purchase after clicking a link on this website, the associate affiliated with this site may earn a comission at no cost to you.

#Advert: Unleash your powers with a Razer laptop.

New Features: Global Quick Tune Internet SDR List Improve Your Radio Knowledge at "YouTube SDR School"
Article Index --- click here to unfold ---
Newest Pages NEW: Trumpists Kicking the Hornets Nest
NEW: Introduction to Catbird Linux
NEW: Skywave Linux Updated to ver 4.1
NEW: i3wm: Using i3-ipc to Float Windows
How to Record from WebSDR and OpenWebRX Sites
Programmatic RTL-SDR Frequency Claibration
Public KiwiSDR Lists
Malaysia Airlines Flight MH17: Simply Mass Murder
The Anonymous Cathay Pacific Employee Letter to Hong Kong
For For Cathay Crews Crossing Borders With Electronics
Photo Gallery 9: The New Life Movement in China, 1944
E Pluribus Unum: From Many, One, Dammit
HFGCS Quick Tune SDR List
The Robert Mueller Iron Triangle Speech
A Rant About One Party Rule
Best OpenWebRX and WebSDR Servers
SDR School via YouTube
ADALM-PlutoSDR on Linux Systems
MOFO Linux: Defeating State Censorship and Surveillance
Linux: Distros, Code, and Nifty Software NEW: Introduction to Catbird Linux
NEW: Skywave Linux Updated to ver 4.1
NEW: i3wm: Using i3-ipc to Float Windows
Skywave Linux: HPSDR, WebSDR, and RTL-SDR ready to run.
Siduction Linux with the Cinnamon Desktop
Siduction Linux with the LXQT Desktop
Andy's Ham Radio Linux 15 and QtRadio
Booting Multiple Linux Disc Images with Grub2
Porteus Linux Hard Drive Installation
UPDATED: MOFO Linux - For Unrestricted Internet
Aptosid with LXDE
Asus EeePC 1215N with Linux
Autostart Tweaks for KDE3 and KDE4
Broadband Speed Tweaks For Linux
Fixing the Firefox 3 Rendering Bug
Linux on Solid State Drives
Linux Wireless Interface Driver Updates
Setting Polkit to Automount USB Devices
Sidux with LXDE
Fixing Skype Inverted Video
SLAX Remix - kernel upgrades
Flash Drive Linux - Introduction
Flash Drive Knoppix 5.3 - Part 1
Flash Drive Knoppix 5.3 - Part 2
Flash Drive Knoppix 6.0 - Part 1
Flash Drive Knoppix 6.0 - Part 2
Flash Drive SLAX - Part 1
Flash Drive SLAX - Part 2
Flash Drive Bluewhite64 - Part 1
Flash Drive Bluewhite64 - Part 2
Flash Drive Linux - Basic Customization
SLAX Customization - Part 1
SLAX Customization - Part 2
Bluewhite64 Customization - Part 1
Bluewhite64 Customization - Part 2
Long Range Wi-Fi Basics of Long Range Wireless Networking
Linear Focus Parabolic Wi Fi Antenna
High Gain Wi Fi Dish Antenna
High Gain Helical Wi Fi Antenna
High Gain Yagi Wi Fi Antenna
High Power Wireless Adapters
Wi Fi Extender Antenna for Routers
Belkin F5D7050 External Wi Fi Antenna
Linksys WUSB54GC External Antenna Mod
Compat Wireless Linux Drivers
Installing WPA_Supplicant for Wi-Fi Security
Linux Wireless Interface Driver Updates
Linux Wireless Interface Driver Support
NetworkManager and Consolekit
RT73 Wireless Drivers for Linux Kernel 2.6.27+
RT2860 Wireless Drivers for Linux Kernel 2.6.27+
Radio: Amateur Radio, Aero Radio, Shortwave, etc NEW: Programmatic RTL-SDR Frequency Claibration
NEW: Public KiwiSDR Lists
NEW: GHFS Quick Tune SDR List
UPDATED: Best OpenWebRX and WebSDR Servers
UPDATED: Skywave Linux: HPSDR, WebSDR, and RTL-SDR ready to run.
CubicSDR on Debian, Ubuntu, and Linux Mint
Dump1090 for Linux Mint 17.1 and Siduction 2014.1
Software Defined Radio - An Introduction
QS1R Direct Sampling SDR
Chaining SDR Audio Interfaces
FLEX-6000 Direct Sampling SDR
UPDATED: RTL2832 Software Defined Radio
WebSDR Digimode Reception
Enabling FLASH in Jack Audio
Realtime Software Audio Processing
Liberation Technology MOFO Linux - For Unrestricted Internet
Veracrypt Encryption for Linux
Veracrypt Encryption for Windows
Using Google Within China
Popcorn Time and Flixtor for Uncensored Streaming Media
DNS Encryption using DNSCrypt
Galaxy Nexus Privacy and Robustness Enhancements
Galaxy SIII Privacy and Robustness Enhancements
Flash Drive Encryption for Linux
Flash Drive Encryption for Windows
Multihop VPN Connections for Strong Internet Privacy
Open and Free DNS Server List
OpenVPN Cloaking against Deep Packet Inspection The Serval Mesh Phone Project
Skype's Robust Security
Man in the Middle Wireless Security Risks
Wireless Security and Surveillance
Digital Audio Adjusting Audio Dynamics in VLC
Backing Track Prep Guide
Ipod Music Processing Guide
How To Record Record Live Music Performances
Realtime Software Audio Processing
Chaining SDR Audio Interfaces
Aerospace Radio, Aviation, Pontification, and Opinion NEW: Trumpists Kicking the Hornets Nest
NEW: The Anonymous Cathay Pacific Employee Letter to Hong Kong
NEW: For For Cathay Crews Crossing Borders With Electronics
NEW: E Pluribus Unum: From Many, One, Dammit
NEW: HFGCS Quick Tune SDR List
NEW: The Robert Mueller Iron Triangle Speech
NEW: A Rant About One Party Rule
Captains Authority Versus Autocratic Airline Management
Malaysia Airlines Flight MH17: Simply Mass Murder
Malaysia Airlines Flight MH370 - A Media Circus
High Gain Air Band Antennas
Apollo Unified S Band Communications
Chinese Anti-Stealth VHF Radar
Oceanic Communications - Procedures, Equipment, Voice and HFDL
Boeing 737NG Radio Equipment
Boeing 767 Radio Equipment
NAOC-TACAMO Monitoring
My Flight on 9/11
Joshua Chamberlain's Leadership Tips
Special Operations Forces Truths
TWA 800: Just Give Me Some Truth
Photo Gallery Aviation Photo Gallery 1: Snapshots From My Journeys
Aviation Photo Gallery 2: On the Road With ATA Airlines
Aviation Photo Gallery 3: More ATA Airlines
Aviation Photo Gallery 4: Southwest Airlines is the Borg Empire
Aviation Photo Gallery 5: Starting Over, Moving On...
Aviation Photo Gallery 6: More Viva Macau
Aviation Photo Gallery 7: Mainland China Airline Flying
Aviation Photo Gallery 8: Chinese Smog and Fog
NEW: Photo Gallery 9: The New Life Movement in China, 1944
Broadcasting BBC Radio Blooper - Adolf Merckle
TV DXing the World Trade Center
New York TV after 9/11
Live Music Recording Adjusting Audio Dynamics in VLC
Backing Track Prep Guide
Ipod Music Processing Guide
How To Record Record Live Music Performances
Radio Poetry and Arts In Distress, by David Wagoner
Just A Radio Operator, by Robert A. Wallace
Radio Circuit Modifications ATS-909 Modifications
ATS-909 Manuals
ATS-909 Alignment Procedure
ATS-909 Alignment Spectrograms
Very Low Frequency (VLF) Radio Internet Based VLF Radio Listening
Windows Tips Windows Performance Enhancement Tips
A Faster Windows 7
Windows 7 SSD Setup

Initially named "Sky Peer-To-Peer" and intended to be a robust, tamper resistant, and decentralized voice-over-internet system, Skype has become the most popular tool for voice communications over the internet. It is easy to install, requires modest bandwidth (33.6 kbps) for good quality voice connections, and offers video and chat as additional means of contact with other Skype users.

Skype is particularly unique in that it offers a means for people to talk to each other through a medium that is difficult for sophisticated surveillance teams to track or monitor. In fact, Skype has been banned in many countries that insist on total control of its communications within their borders. Therefore Skype is a favorite of all people who value privacy. Presented here is a summary of the strengths and weaknesses of Skype as it relates to defending the users' privacy from surveillance from all others not a party to the communications. It will be shown that Skype is resistant to wiretapping, but the chat and voice data is vulnerable to capture by spyware prior to encryption and entry to the Skype network.

Skype's Main Strengths:

  1. Designed to use decentralized peer-to-peer connections (nodes and supernodes).
    • Skype cannot be disabled by blocking IP addresses.
    • Data flows difficult to trace or capture due to very adaptable routing scheme.
  2. Strong encryption using 256 bit public key and symmetric protocalls.
    • Unlikely, in the history of human existence, to be broken by a brute force attack.
    • Fast key creation on modern hardware.
    • Encryption protocalls well known and found to be quite secure.
  3. Flexible use of ports - diffuicult to block with firewalls.

Skype does have some vulnerabilities, mostly due to its operating environment on computers subject to spyware and malware installations. Users failing to regularly scan and disinfect their computers are especially vulnerable to having their activities monitored or blocked.

#Advert: Supercharge your computing on systems and parts from Eluktronics

Skypes Main Weaknesses:

  1. Skype's inner workings are proprietary and closed sourced.
    • No trusted third party analysis of the whole system's resistance to sophisticated attacks.
    • Without the ability to study the software, backdoors for surveillance can't be reliably detected.
  2. Skype can't get exclusive access to the audio data within users' computers.
    • Audio or chat can be captured, prior to encryption, by spyware designed to detect skype calls.
    • Captured audio or chat can be archived by spyware for use by adversaries.
  3. Data packets can be detected, blocked or captured using deep packet inspection.
  4. Some activity is easily detected and blocked, such as the login process.

Monitoring a computer's TCP and UDP traffic reveals the login exchange between the local application and the remote server. Skype transmits the following 5 byte message to the server: 0x1603010000. Then the server replies with this 5 byte message: 0x1703010000. Detect and block incoming packets containing the sequence 0x1703010000 and Skype is disabled. Also, there are skype fingerprints in the public key exchange messages at the start of a connection. The client to server key exchange SSL message begins with 0x160301, indicating a key exchange using SSL version 3.1. Receiving this, the server responds with a message using a non-SSL based header: 0x170301. Detect and block packets containing the header 0x170301 and skype is disabled.

Skype Blocking Software

There are Skype filters which detect the skype protocol and / or traffic on ports used by Skype. The most effective use deep packet inspection to find and block the data packets, while simply blocking the most commonly used ports causes skype to fall back on passing data as http packets. Port blocking is the least effective, due to skype's ability to use any of a huge range of ports!

Skype Blocking Software Vendors:

Bitek International Inc.USA
Lynanda CSCountry
Narus Inc.USA
Verso TechnologiesUSA

In some cases, the attacker's goal is not blocking or interrupting the use of Skype, but instead conducting a wiretap. Spyware is covertly installed on the target's computer and gains access to the communications in unencrypted form. Such anti-Skype spyware is useless in situations where the users have encryption devices external to the computer system hosting Skype.

Users in China or making calls to users in China need to be aware that TOM-Skype is compromised software. It enables full wiretapping by the PRC, and is subject to sophisticated tracking and keyword scanning. It contains internal and downloaded Chinese keyword lists. Do not useit under any circumstances. Because Skype's website redirects visitors from China to TOM-Skype, one must use a VPN to get the regular software. Otherwise, download from the Skype beta page which is accessible directly from within China.

Skype Spyware Vendors:

NamePublisherSkype Vulnerability Exploited
FinSpyGamma International UK Ltd.Captures audio directly from audio interface.
TOM-SkypeTOM Group LtdSpecial version of Skype for China, captures and filters text and chat.
HackingTeam SRL (Milan Hackers)Captures audio directly from audio interface.
Gamma (German Hackers)Captures audio directly from audio interface.
DigiTask GmbHCaptures audio directly from audio interface.
ERA IT Solutions AGCaptures audio directly from audio interface.

The number of companies seeking to make huge profits from the sale of anti-Skype software tells us something about human nature: for every tool created to connect people and decentralize connectivity (and the associated empowerment), there are other adversarial tools created by those seeking wealth by catering to governments and organizations interested in disconnecting people while centralizing and controlling communication (thereby taking power and freedom from people). Countries such as Ethiopia have gone so far as to criminalize the use of Skype. In truth, the use of Skype can be effectively concealed and conversations protected even in Skype-hostile countries, if proper measures are taken.

Many measures can be taken to render ineffective the types of anti-Skype software listed above. The focus of defending communications through Skype is to keep spyware / malware off of the Skype user's computer and to make Skype data difficult to detect and block. Below is a list of ways to defend Skype communications from eavesdropping and blocking:

  1. Never, EVER, use TOM-Skype and do not connect to users of TOM-Skype
  2. Use a VPN to prevent detection of Skype calls.
  3. Use a VPN to further protect the data stream from cryptanalysis.
  4. Keep your system free of spyware / malware.
  5. Use Linux or Linux with WINE to run Skype - the spyware / malware is almost exclusively Windows!!
  6. Use a live CD like knoppix or slax, with Skype installed, that can't be infected or altered by spyware or malware.
  7. Use an external audio encryption tool to encode / decode conversations.

After considering the above information on Skype, one can feel secure using it as a means of sharing sensitive information under specific controlled conditions. Specifically, both users should use computers known to be free of spyware or malware. An operating system other than Microsoft Windows is safer, but should still be regularly scanned and purged of rootkits or other unwanted tools of surveillance agencies. Network communications security is only as strong as its weakest link. Except for TOM-Skype, the things putting Skype users at risk are external to Skype and not a factor on a well maintained computer system.

Further Reading on the Strength of Skype Security:

TOM Skype Is Spyware!!
TOM Skype Research
Inferring Speech Activity from Encrypted Skype Traffic
A Study of Skype Blocking Methods
Skype Protocol Analysis
Skype Relay Analysis
Tracking Skype Traffic

Tags: skype security, insecure skype, skype cracks, skype flaws, skype hacks

©2005 - 2020 AB9IL, All Rights Reserved.
About, Contact, Privacy Policy and Affiliate Disclosure, XML Sitemap.