# Verification During Attack Situations > As such, the verification is reliable as long as honest nodes control the network, but is more vulnerable if the network is overpowered by an attacker. > > \- Satoshi Nakamoto, Bitcoin Whitepaper ![](/files/Zqn9u83YPQ6buXRCxvtf) If the network is overpowered by an attacker who is extending the longest chain of proof of work upon an invalid block (either a block that contains an invalid transaction or which doesn’t comply with some other aspect of the network’s rules) user wallets will be unable to determine that the longest chain is not the longest *valid* chain of proof of work. In this instance it would be possible for the attacker to present information about an invalid transaction that would imply that it had been accepted into the longest chain of proof of work and built upon by the majority of network CPUs. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://hub.bsvblockchain.org/higher-learning/bsv-academy/bsv-theory/simplified-payment-verification/verification-during-attack-situations.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.