user537: What happened to this transaction?
Can someone explain it?
http://blockexplorer.com/t/9eHTFRi3Qq

user81: 
On July 29 2010, it was discovered that block 71036 contained several transactions with a ton of OP_CHECKSIG commands. There should only ever be one such command. This caused every node to do extra unnecessary work, and it could have been used as a denial-of-service attack. A new version of Bitcoin was quickly released. The new version did not cause a fork on the main network, though it did cause one on the test network (where someone had played around with the attack more).

https://en.bitcoin.it/wiki/Incidents#OP_CHECKSIG_abuse

537: <p>What happened to this transaction?</p>

<p>Can someone explain it?</p>

<p><a href="http://blockexplorer.com/t/9eHTFRi3Qq" rel="nofollow">http://blockexplorer.com/t/9eHTFRi3Qq</a></p>
 81: <blockquote>
  <p>On July 29 2010, it was discovered that block 71036 contained several transactions with a ton of OP_CHECKSIG commands. There should only ever be one such command. This caused every node to do extra unnecessary work, and it could have been used as a denial-of-service attack. A new version of Bitcoin was quickly released. The new version did not cause a fork on the main network, though it did cause one on the test network (where someone had played around with the attack more).</p>
</blockquote>

<p><a href="https://en.bitcoin.it/wiki/Incidents#OP_CHECKSIG_abuse">https://en.bitcoin.it/wiki/Incidents#OP_CHECKSIG_abuse</a></p>
