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Author Topic: Electrum 1.7.3 connects to many different IP addresses on startup. Why?  (Read 2198 times)
DigitalHermit
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May 14, 2013, 04:53:25 PM
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Hello,

  This is a basic question about Electrum security. I run my own electrum server and have configured electrum to only connect to it (no looking for random other servers if my server is unavailable). So, that being the case, why does electrum need to connect to a bunch of other IP addresses on startup?

So far I've logged the following (in IP:port format):

204.232.175.78:80
190.93.243.195:80
141.101.112.196:80

Before I get out my proxy server and start pouring over the source code to figure out what it is trying to do, anyone know why electrum would need to connect to all these different IP address? It seems to be chatty for no apparent reason.

Thanks!

p.s. none of these IP addresses is my electrum server btw.
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May 14, 2013, 04:57:10 PM
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One is probably looking for updates at github to tell you of a new updates, another is to look up the exchange rate. Not sure what the 3rd might be.

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May 14, 2013, 05:30:31 PM
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the 3rd is the connection to electrum.org to download the blockchain headers

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May 14, 2013, 05:45:37 PM
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Thanks for the explanation(s)!

I always thought that the client was downloading blockchain headers from the electrum server but obviously my assumption was incorrect. Doesn't that make all electrum clients vulnerable to the shutdown of the electrum.org site then? Seems fragile at the least.

The other two queries (new version check and currency exchange rate check) seem like they could be made optional (with a command line option of some sort). Perhaps if I have time I'll fork a version that has that feature.

p.s. The reason I noticed these is that the electrum gui failed to come up sometimes (seemingly randomly) and so I started troubleshooting the network - turns out my network was being spotty.
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May 14, 2013, 05:54:34 PM
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Thanks for the explanation(s)!

I always thought that the client was downloading blockchain headers from the electrum server but obviously my assumption was incorrect. Doesn't that make all electrum clients vulnerable to the shutdown of the electrum.org site then? Seems fragile at the least.
if you install Electrum for the first time, it will try to download the headers from electrum.org.
if this fails, it will query them from the servers.
this is in order to reduce the load on the servers.


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May 14, 2013, 10:06:11 PM
 #6

In case anyone reading this thread with electrum installed on linux wants to prevent these connections without altering electrum source code directly, this shell script did the trick (assuming you have admin access to your linux box):

Code:
#!/bin/sh

# Block outbound access temporarily
sudo iptables -A OUTPUT -d 204.232.175.78 -j DROP
sudo iptables -A OUTPUT -d 190.93.243.195 -j DROP
sudo iptables -A OUTPUT -d 141.101.112.196 -j DROP

# Run electrum
/usr/local/bin/electrum

# Unblock outbound access
sudo iptables -D OUTPUT -d 204.232.175.78 -j DROP
sudo iptables -D OUTPUT -d 190.93.243.195 -j DROP
sudo iptables -D OUTPUT -d 141.101.112.196 -j DROP
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May 17, 2013, 04:22:40 AM
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One is probably looking for updates at github to tell you of a new updates, another is to look up the exchange rate. Not sure what the 3rd might be.
The third is probably the Electrum servers themselves.
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