Bad Checksum reported on all Updates

[abrogard]

I've got Spybot 1.4 and tried to use it for the first time here today. It urged me to check for updates and download them so I tried to do that.

I had about five updates to download: detection rules, english,etc., etc.,

Every single one failed with a report (within Spybot) of 'Bad Checksum'.

Anyone got any clues?

I've got AVG and Sygate guarding the computer.

regards,

ab

[dk2005]

Refer to this faq: http://www.safer-networking.org/en/faq/20.html

I always use BN fileforum server, it always work well for me.

Cheers

[nexuswest]

This has been a relatively frequent problem that I usually could resolve by changing download site. Often I had to try more than one before downloading successfully. The site that worked previously wouldn't always succeed the next time.

Related note: the "bad checksum" text message to the right of the "bad" or "green check mark" icon would not go away after successful download if the same download had failed previously. I inferred success from the green check mark, and the disappearance of the "bad" icon.

Any insight into the cause of this relatively frequent occurance would be welcome, as it is a unique problem to downloads with S&D (no similar problem with SpySweeper, LavaSoft or NAV).

Tx,

Robert

[masu1]

is there a way to autodelete servers from update list which have bad checksums?

[nexuswest]

I caution against auto-deleting servers that exhibit the bad checksum behavior, as this problem can arise and then disappear. A reasonable scenaro would have you auto-delete all servers, only to have the problem correct itself once you were no longer able to reach any servers...

I agree that the problem is frustrating and time-wasting. I hope that someone from the S&D team will take a moment to explain the cause and indicate what they are doing to correct the problem.

Robert

[masu1]

it's not just annoying

personally I feel unsafe. I think a trojan or a virus have manipulated the checksum.

[md usa spybot fan]

is there a way to autodelete servers from update list which have bad checksums?
No but: The download server can be changed after the "Search for Updates" and before clicking "Download Updates". So if you find a server that works well, you can start by using that server in the future. Also note that if you want (not necessarily recommended) you can select a server and then right click on the button and "Set this server as the preferred download location". If you do that Spybot will select that sever rather than a random (see Note #1) server for future updates.

Note #1: Spybot 1.4 selects a random server. Spybot 1.3 always selects the first server which is currently See-Cure #1 (Europe). This places the heaviest load on that server increasing the likelihood of getting "Bad Checksums" when using See-Cure #1 (Europe).

[masu1]

if so the error message should be

servertraffic is too high, please use another server from the list

and not CRC error

[nexuswest]

Hmmm, interesting, start with user selected preference, then make a random selection if that fails? Or add an option to use most recent successful server first. Unfortunately I don't know what the "bad checksum" error actually means... does it indicate a communication failure with an overloaded server, for example, that is "seen" as a result file that does not validate because it's missing some part? Feel like I need to understand more about the underlying cause to make sense of this.

[md usa spybot fan]

Unfortunately I don't know what the "bad checksum" error actually means... does it indicate a communication failure with an overloaded server, for example, that is "seen" as a result file that does not validate because it's missing some part?
It can be because the file is not complete or it can be because the download server was not updated properly and the wrong file was received.

For more of an explaination see:
http://forums.spybot.info/showpost.php?p=7798&postcount=5

[bitman]

Hmmm, interesting, start with user selected preference, then make a random selection if that fails? Or add an option to use most recent successful server first.
Since at this point none of this logic exists, this idea is as good as any. The real problem, however, is download server bandwidth as mentioned by md usa spybot fan in the post he referenced above. Methods for reducing this load like incremental updates should probably be the first priority.


Unfortunately I don't know what the "bad checksum" error actually means... does it indicate a communication failure with an overloaded server, for example, that is "seen" as a result file that does not validate because it's missing some part? Feel like I need to understand more about the underlying cause to make sense of this.
As already mentioned, this can be due to any number of issues, not just the server itself. Since the initial SpybotSD.ini control file is downloaded from a different server, almost anything that can fail will cause this message. This is because the client has no way to determine what really failed, since the download takes place in the control of Windows, not Spybot. Spybot only gains control of the file at the point the download completes or fails due to timeout, so all it can do is check the file's integrity using the checksum, thus the Bad Checksum error message.

A Technique has already been discussed elsewhere of detecting a currently unavailable server by downloading a small file and verifying it's checksum, then switching to another (random or sequential) server if that fails. Adding additional 'smarts' to this would make sense, but the core problem is detection of a failed or more so a very slow responding server before attempting a large download such as the 1MB Includes (detections) file.

Until such major changes can be made to the Spybot program, it's best to choose the most effective server available. Though the two 'Safer Networking' servers in Europe are typically very fast, they may not be the most reliable due to a special case.

The 'BN FileForum (World)' is actually several servers placed in strategic locations around the world (4 in the US), so if one fails, others are already available to take over for the failed server. Even though these servers are often not the fastest (best bandwidth), especially in Europe or Asia/Pacific due to inefficient peering by local ISPs, they should be the most available.

Using the "Set this server as the preferred download location" with the BN FileForum (World) selection should result in the highest probablility of success. Since there are multiple servers worldwide and a failure is dealt with via network routing, it's designed to deal with the most likely failure scenarios, including some ISP peering or router failures.

[nexuswest]

Wanted to thank member DK2005 for posting a URL with an explanation of the cause. I had several replies in close sequence today, and missed this post that probably came in before I was asking about likely causes. Bottom line is "server busy", but the link is worth reading b/c S&D has answered that question clearly.

Again, thanks!!!

Robert