Last week, an unknown actor sent a deluge of spam that left bitcoin's nodes – the clients that store and relay transactions – with upwards
of 88,000, or 1GB worth, waiting in their collective memory pool.

Today, despite the memory pool returning to normal (around 4MB at press time) and Core developer Jeff Garzik implementing a 'quick fix' for operators,
the total number of reachable nodes – 5,030 – remains 16% lower than before the 'attack'.