Griefing Attacks: Are they profitable for the attacker?

Question

The following article explains one of the solutions for indirectly validate a block when cross-sharding transaction between two shards to prevent invalid blocks.

The article called one of these solutions "Fisherman" (without any more explanation about the term Fisherman in more details ...)

The article then mentions that the Fisherman (as a dominant solution) has two problems, one of which is as follows:

"The existence of the challenge protocol creates a new vector of attacks when malicious nodes spam with invalid challenges. An obvious solution to this problem is to make challengers deposit some amount of tokens that are returned if the challenge is valid. This is only a partial solution, as it might still be beneficial for the adversary to spam the system (and burn the deposits) with invalid challenges, for example to prevent the valid challenge from a honest validator from going through. These attacks are called Griefing Attacks."

Link to the article: https://medium.com/nearprotocol/unsolved-problems-in-blockchain-sharding-2327d6517f43

Although, the article says that this attack, called "Griefing Attacks" might still be beneficial for the adversary, but in this answer (here: https://ethereum.stackexchange.com/a/62846/23024) says:

"Such an attack doesn't benefit the attacker ..."

So, eventually,

• (1) Is Griefing Attacks profitable for the attacker or not?

• (2) What is the exact definition of Griefing Attacks?

Please note that this question is different with another question (https://ethereum.stackexchange.com/a/62846/23024) that I have linked in my question. Because: (1) That question is: "What does Griefing mean?" but my question is: "Are Griefing attacks profitable for the attacker?" Also (2) I linked to that question, where I said that while in the answer of that question is mentioned: "Such an attack doesn't benefit the attacker ...", but in another article is said: "Griefing attacks might still be beneficial for the adversary". So the question is that eventually Griefing attacks are profitable or not? It might cause to define precisely Griefing attacks.

Answer 1

I'm really not very familiar with griefing attacks but based on the definition I'd say they can be profitable for the attacker. Not directly but indirectly.

My not-too-scientific analysis is based on the example given in the linked answer's references: https://consensys.github.io/smart-contract-best-practices/known_attacks/#insufficient-gas-griefing

This is not a perfect example but at least something: imagine a contract which is used for finding out whether anyone disagrees or agrees with some idea. So a maximum of one "yes" and a maximum of one "no" is enough for the contract. Now for some reason it needs to be called through such a Relayer contract. If the attacker performs a griefing attack on the "yes" or the "no" answer the answer doesn't get stored but nobody else can give that answer anymore as the Relayer has already blocked that answer. That way the attacker knows nobody can give an answer he doesn't like.