<blockquote>
  <p>[The miner] edits code of bitcoin software to set his own verification rules for transactions so that he can bypass all the invalid transactions from his accomplices to mempool. Is it possible?</p>
</blockquote>

<p>Yes and no. </p>

<p>Yes, it is entirely possible to modify the code to include whatever sort of transaction validation rules you want. </p>

<p>No, you cannot use this to trick the rest of the network into accepting your invalid transactions. Your node would be banned by other nodes in the network, since it is not following the rules of the network. The network is formed by the connections of thousands of individual nodes, that all follow the same rules. If a node breaks those rules, then the rest of the network will simply ignore them. </p>

<p>By changing the validation/consensus rules, you would effectively be creating a new altcoin network.</p>

CC BY-SA 3.0
2018-03-08T00:21:32.747Z
I would like to add that there's not a single mempool, but as many different mempools as miners
Osias Jota
CC BY-SA 3.0
2018-03-08T01:17:51.837Z
@OsiasJota that is indeed a point worth noting, however there are many more individual mempools than there are miners. The majority of full nodes likely keep their own local mempools as well.
chytrik
CC BY-SA 3.0
2018-03-07T23:51:22.250Z
2018-03-07T23:51:22.250Z
chytrik
<p>While the attacker can modify their software any way they like, the attacker would only hurt themselves. <strong>Full</strong> nodes are named such for their feature to "fully enforce all consensus rules of Bitcoin independently". Every full node maintains their own mempool. Since the "fake transaction" you've suggested obviously does not adhere to the consensus rules, every other node would simply reject the transaction as invalid and then ban the node that relayed it to them.</p>

CC BY-SA 3.0
2018-04-24T02:54:14.430Z
2018-04-24T03:25:07.073Z
2018-04-24T03:25:07.073Z
Murch
<p>Is it possible for a malicious attacker to download a bitcoin software code, modify that code and use that software for his own benefit? I know that any changes implemented in the bitcoin software must be accepted by the majority nodes in the bitcoin network. But, here, consider that the malicious attacker doesn't need to use that modified version of bitcoin software by other users.</p>

<p>Here is an example, Suppose B is a malicious miner. He wants to modify the verification conditions(20 rules) of transactions. Then, he edits the code of bitcoin software to set his own verification rules for transactions so that he can bypass all the invalid transactions from his accomplices to mempool. Is it possible?       </p>

<transaction-verification><consensus>
Can an attacker use a modified Bitcoin node to pass fake transactions into the mempool?
Monmoy Sarker
# Can an attacker use a modified Bitcoin node to pass fake transactions into the mempool?

(Asked by: username_0 on 2018-03-07)

Is it possible for a malicious attacker to download a bitcoin software code, modify that code and use that software for his own benefit? I know that any changes implemented in the bitcoin software must be accepted by the majority nodes in the bitcoin network. But, here, consider that the malicious attacker doesn't need to use that modified version of bitcoin software by other users.

Here is an example, Suppose B is a malicious miner. He wants to modify the verification conditions(20 rules) of transactions. Then, he edits the code of bitcoin software to set his own verification rules for transactions so that he can bypass all the invalid transactions from his accomplices to mempool. Is it possible?

**Tags:** transaction-verification, consensus


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## 2 answers

### Answer by username_1 on 2018-03-07. Score: 2

> [The miner] edits code of bitcoin software to set his own verification rules for transactions so that he can bypass all the invalid transactions from his accomplices to mempool. Is it possible?

Yes and no.

Yes, it is entirely possible to modify the code to include whatever sort of transaction validation rules you want.

No, you cannot use this to trick the rest of the network into accepting your invalid transactions. Your node would be banned by other nodes in the network, since it is not following the rules of the network. The network is formed by the connections of thousands of individual nodes, that all follow the same rules. If a node breaks those rules, then the rest of the network will simply ignore them.

By changing the validation/consensus rules, you would effectively be creating a new altcoin network.

> **Comments:**
> **username_2**: I would like to add that there's not a single mempool, but as many different mempools as miners  
> **username_1**: @username_2 that is indeed a point worth noting, however there are many more individual mempools than there are miners. The majority of full nodes likely keep their own local mempools as well.  

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### Answer by username_3 on 2018-04-24. Score: 2

While the attacker can modify their software any way they like, the attacker would only hurt themselves. **Full** nodes are named such for their feature to "fully enforce all consensus rules of Bitcoin independently". Every full node maintains their own mempool. Since the "fake transaction" you've suggested obviously does not adhere to the consensus rules, every other node would simply reject the transaction as invalid and then ban the node that relayed it to them.


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