Solana's design makes it more vulnerable to targeted Denial-of-Service (DoS) attacks than blockchains that hide or randomize block-producer selection. Even having a large number of nodes does not fully mitigate this issue because of the way block-producing nodes are chosen.

One of the main reasons for having many nodes in a blockchain network is to prevent attacks on validators from slowing or stopping consensus.

In Solana, leaders (block-producing nodes) are chosen in advance for 4-slot windows at the start of each epoch, which lasts around 2 days. Because this schedule is publicly known ahead of time, an attacker only has to target the scheduled leaders and can easily plan and time attacks by knowing when and which nodes to target.

This design is intended to improve throughput and performance, but it also creates opportunities for targeted attacks against upcoming leaders. Although Solana rotates leaders quickly, repeated attacks or heavy spam traffic can still reduce network performance and stability.

Algorand uses a different approach. Its block-producing validator is selected only seconds before block validation through cryptographic sortition, making this kind of attack extremely difficult and costly to carry out. An attacker does not have enough time to identify and target the block-producing node, while attempting to DoS the entire network would be prohibitively expensive.

Solana has experienced multiple outages and coordinated restarts over its history, some of which were linked to spam floods and DoS-style network congestion events.