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  Is Skype (mis)using your computer?
Experiences Posted by Fabian Wenk on Tuesday January 25, @01:15PM
from the free-does-not-mean-it-cost-nothing dept.
Last week our mail account for support got an email from somebody from Luxembourg asking why his computer has a open connection to one of our computers. The connection was not to one of our servers (which is quite common) but to TCP port 4617 on a regular computer in an office. Read on for more...

I walked over to the office where this computer is, to have a look at it and found the free Internet telephony from Skype running on it. For our international co-worker this seems to be an affordable way to talk to their relatives at home without expensive international phone calls.

After further checking this computer with netstat and Fport (from Foundstone) I had a detailed look at the TCP ports 80 (http), 443 (https) and 4617 which are not so common open on a users workstation. The output from netstat shows some connections to the local TCP port 4617 especially from some dial up and end user internet connections (*.adsl.xs4all.nl, *.pool80182.interbusiness.it, *.user.veloxzone.com.br and *.mundivox.com) and from some random IP addresses. In the output from Fport it is clear, that this connections are going to the Skype software.

As far as this looks like to me, Skype is using some kind of peer-to-peer like distributed network of "servers", actually the computers of their own users/customers to distribute the connections from their other customers so they do not solely need to depend on the availability of Skype's own servers and performance. I had not to read very far in the Skype End User License Agreement until to get to Article 4. Permission to Utilize on which the following proved my guess:

4.1 Permission to utilize Your computer. In order to receive the benefits provided by the Skype Software, you hereby grant permission for the Skype Software to utilize the processor and bandwidth of Your computer for the limited purpose of facilitating the communication between You and other Skype Software users.

Yesterday there was a discussion started on the Full-Disclosure security mailing list with the Subject blocking SkyPE?, also some follow-up postings are very interessting, eg. this from Alain Fauconnet and this answer from Bryan K. Watson and then this from Alain Fauconnet again.

From my point of view I'm glad I did not use this software even though it was suggested to me personally. In the first place I did not like the proprietary approach of Skype's solution even if they provide cost free service and a cost free software. But the protocol they use to communicate is not free, so users/customers of this service depend on Skype as long as they want to use it. Also Skype has the freedom to change their policy any day and charge for their currently free services.

With this "anonymous" use of the computers at our site (Swiss Federal Institute of Technology Zurich) we probably will have some legal problems in the future. So think twice if you really want to use such "free" services like Skype's Internet telephony.

ETH Zurich provides informations about alternatives on the Videoconferencing website. There is client software available which support the open H.323 protocol standard, eg. GnomeMeeting on Linux and other OpenSource unix alike operating sytems, XMeeting on Apple MacOS X and Netmeeting already delivered with Microsoft Windows (see here for changes needed to run it properly on Windows XP).

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    The Fine Print: The following comments are owned by whoever posted them.
    ( Reply )

    Over 10 comments listed. Printing out index only.
    Re: Is Skype (mis)using your computer?
    by UltraPeer on Tuesday January 25, @07:13PM
    as much as i know, the open connections come from the fact that skype even works with two people residing in masqueraded/filtered networks. they just communicate over an ultra-peer with a public ip-address. skype always tries to select the best ultra-peer for two hosts. so, this is just the old, standard ultrapeer thing like it is also used for gnutella.

    and of course, as the eth has a quite nice network and almost all machines have public ip's, i don't wonder that they get selected as ultrapeers
    [ Reply to this ]
    Re: Is Skype (mis)using your computer?
    by Robert Jordens on Wednesday January 26, @09:43AM
    Also worth mentioning as an alternative to both H.323 and Skype is SIP. Service providers include the ETH (sipETH), and others (web.de, Sipgate ...). Usable clients are fore example Linphone, KPhone. There are also feature-rich and production-quality Open Source SIP/H.323 servers like Asterisk and Bayonne. Communication between SIP devices is free (apart from Network costs), the service providers offer uplinks to the PSTN for a fee. SIP also works behind NAT.
    [ Reply to this ]
    Re: Is Skype (mis)using your computer?
    by D'uh! on Wednesday January 26, @09:11PM
    This is how Skype works and it's public knowledge. Skype uses the P2P network created by the users to route voice traffic. They even say so on their homepage: http://www.skype.com/products/explained.html
    [ Reply to this ]
    Re: Is Skype (mis)using your computer?
    by Ernest Opitz on Monday April 25, @10:01PM
    Is skype misusing my computer? I'm not a geek or a nurd! I really don't know!
    [ Reply to this ]
    Re: Is Skype (mis)using your computer?
    by Ernest Opitz on Monday April 25, @10:01PM
    Is skype misusing my computer? I'm not a geek or a nurd! I really don't know!
    [ Reply to this ]
    Re: Is Skype (mis)using your computer? Naturally !
    by TheoTester on Thursday August 25, @10:59PM
    OFF COURSE is Skype (mis)using your computer.

    Actually, the more idle time and power your computer has, the more it will be utilized.

    Its the whole idea of Skype: Some people (=Skype most and each of their users a bit) benefit from the investment that other people make (Computer Owners, all people who actually have to pay for data centers, telecommunication bandwith, existing Network Equipment, in short: They'd be dead if the infrastructure wasn't paid by you through tyes and phone bills.

    They create and contribute close to nothingm but they live from shaving off a tiny little profit from every skype out connection they handle.

    Funny enough: They actually destroy the value chain that keeps the infrastructure going (and that feeds them). In the end they are really more like a desease of the networks, some kind of parasite organism that doen't care if it destroys the ressources of its host.

    They live by the process of redistributing routing, CPU power and bandwith from the same people they serve, they steal performance and bandwidth from public networks and shave off their profit from termination fees they are anabled to collect by standards and agreements that those public phone networks have made for their fair interworking - which is exatly that what they are working hard for to destroy it.

    They steal your cpu, bandwidth, and routing performance together with that of all the internet community and redistribute it somwhere else, deminusished by the performance neede to run their product.

    When performance based computing and computing on demand becomes commonplace, skype will dry out, as computer performance will be openly available, but at a cost. Noone will feed suckers like Skype for free anymore, if their not stupid.

    Some info about what Skype does: http://www1.cs.columbia.edu/~library/TR-repository/reports/reports-2004/cucs-039-04.pdf
    [ Reply to this ]
    Re: Is Skype (mis)using your computer? Naturally !
    by TheoTester on Friday August 26, @09:17PM
    OFF COURSE is Skype (mis)using your computer.

    Actually, the more idle time and power your computer has, the more it will be utilized.

    Its the whole idea of Skype: Some people (=Skype most and each of their users a bit) benefit from the investment that other people make (Computer Owners, all people who actually have to pay for data centers, telecommunication bandwith, existing Network Equipment, in short: They'd be dead if the infrastructure wasn't paid by you through tyes and phone bills.

    They create and contribute close to nothingm but they live from shaving off a tiny little profit from every skype out connection they handle.

    Funny enough: They actually destroy the value chain that keeps the infrastructure going (and that feeds them). In the end they are really more like a desease of the networks, some kind of parasite organism that doen't care if it destroys the ressources of its host.

    They live by the process of redistributing routing, CPU power and bandwith from the same people they serve, they steal performance and bandwidth from public networks and shave off their profit from termination fees they are anabled to collect by standards and agreements that those public phone networks have made for their fair interworking - which is exatly that what they are working hard for to destroy it.

    They steal your cpu, bandwidth, and routing performance together with that of all the internet community and redistribute it somwhere else, deminusished by the performance neede to run their product.

    When performance based computing and computing on demand becomes commonplace, skype will dry out, as computer performance will be openly available, but at a cost. Noone will feed suckers like Skype for free anymore, if their not stupid.

    Some info about what Skype does: http://www1.cs.columbia.edu/~library/TR-repository/reports/reports-2004/cucs-039-04.pdf
    [ Reply to this ]
    Re: Is Skype (mis)using your computer?
    by Tobi on Tuesday August 15, @02:20PM
    @Theo: This is one of the most unqualified comments I've ever read.
    [ Reply to this ]
    Re: Is Skype (mis)using your computer?
    by Leo Ashcraft on Monday October 30, @11:24AM
    Well, I see what you're saying, but I havn't had any problems, as long as they can hide it and I don't have to deal with it while I'm on the computer, besides, I don't usually leave my programs running. It hasn't been a problem for me(even though I do have a top line computer, lol) at about 3 ghz, I would hope it wouldn't slow me down, talk about speed, lol.
    [ Reply to this ]
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