A version of the ethereum blockchain being used by developers to test a forthcoming network upgrade is under spam attack.

Beginning almost as soon as development began on the Ropsten testnet, the disruptions come at a time when developers are testing new code called Byzantium, an upcoming hard fork that will ring in the platform's third stage of development.

However, despite the fact that the hard fork is planned for October 17, developers say there's no reason to believe the attacker will delay time-sensitive work. That's not to say there couldn't be complications, though. 

During a test period, ethereum developers use an alternate version of the blockchain to test the accuracy of new code. Ropsten is one of three, but it's an important one as it is the only testnet which allows both main ethereum clients, Geth and Parity. In short, unlike other testnets that are meant for more experimental features, Ropsten is unique in that it mimics the proof-of-work consensus model popularized by bitcoin and that ethereum uses today.

Looking for another option, the spam attack has pushed some developers into a more secure test environment, Rinkeby, though this appears as though it could have implications for the work.

Speaking in an online forum, Raiden developer Lefteris Karapetsas touched on the issue, describing Ropsten as the "closest thing to the mainnet" and stating this similarity can provide better testing conditions.

Karapetsas stated:

The attack, which can be witnessed here, consists of a Ropsten address swarming the blockchain with thousands of auto-generated, faulty transactions.

Since the start, the attacks have continued in waves, leading the spammer and the developers into a game of cat-and-mouse to keep the fake transactions from interrupting the network.

But since so few miners run the software necessary to power the test blockchain, attacks are relatively easy. To this effect, a similar attack was documented in March of this year, an event which actually forced developers to rewrite the Ropsten blockchain.

At the time of writing, developers seemed to have successfully staved off the attacker by raising the cost of transactions. However, developers were also impacted by the price increase and have been unable to run tests, documenting their frustration on social media. 

Luckily, ethereum developer Casey Detrio believes the attacker will not delay the Byzantium test period. He told CoinDesk: "It's only a distraction and inconvenience."

On top of that, it's not exactly clear to ethereum developers why someone would attack a test blockchain. Unlike attacks on the mainchain, the ether used on Ropsten is a test currency, and has no value its own right.

As such, it's hard to imagine what the incentive is to attack, beyond malignant trolling.

Detrio told CoinDesk: "I imagine they get a kick out of it."

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