Over the past 24 hours, the blockchain has been inundated with small, spam-like transactions that are large in data size, but significantly small in bitcoin value transferred.
At the peak, there were more than 50,000 unconfirmed transactions waiting to be mined into a block, resulting in delays for normal transactions to be confirmed. While the network has been working to decrease this backlog — transactions are down to 31,000 at time of this article’s writing — the type of transactions that are being sent suggest this is a continuation of a stress test that has been put on the system.
There have been numerous transactions hitting the network with tiny transaction values, such as 0.0001 bitcoin being sent repeatedly. While not every transaction has been this exact size, there have been numerous others sent every second, reaching hundreds of transactions per second at the peak.
Further, the physical sizes of these transactions are significantly greater than other ones with far more value. Due to the 1 megabyte cap on block size, the mining network has found it difficult to process all these small transactions.
In the past several weeks, similar stress tests have been run to inform the debate about whether to increase the total size of a block. Many argue that increasing it past 1 megabyte would be disastrous to the system. However, Gavin Andresen has argued for increasing it to 20 megabytes so that more total transactions could fit within one block, thus preventing scenarios and delays like are currently being seen.
The current proposed solution by some miners has been to raise it to 8 megabytes. Others have suggested the implementation of the Bitcoin Lightning Network, which is in development to implement hashed time-lock contracts between people.
Update on 7/8/2015 at 10AM EST: Despite early attempts to decrease the number of backlogged transactions, TradeBlock revealed today that there are currently over 81,000 unconfirmed transactions, due to the continued spam transactions being transferred. LocalBitcoins sent out a tweet to its followers this morning urging customers to increase the transfer fee when transferring to the company so that miners are incentivized to process those transactions are first.
If you're sending #bitcoin to LocalBitcoins put a higher fee than the default to avoid having to wait because of the #blockchain spam attack— LocalBitcoins.com (@LocalBitcoins) July 8, 2015
Read more about how wallet companies are responding to this disruption.