A version of the Ethereum blockchain used to test a forthcoming network upgrade is reported being under spam attack.

The attack consists of a Ropsten address swarming the blockchain with thousands of auto-generated, faulty transactions. Since its 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". 

At the time of writing, it seems that the developers have successfully staved off the attacker by raising the cost of transactions. Ethereum developer Casey Detrio believes the attacker will not delay the Byzantium test period. The man told to on coindesk.com:

It's only a distraction and inconvenience.
 

Casey Detrio
Ethereum developer 

Still, it's not exactly clear to the developers why someone would attack a test blockchain.  The disruptions occurred when the developers were testing Byzantium, an upcoming hard fork of the platform. As reported, the spam attack resulted in turning of some developers into a more secure test environment, Rinkeby.

The developers assure there's no reason to believe the attacker will delay the hardfork, which is planned for October 17th.