Spamhaus servers were hit with a huge amount of data via an attack technique known as a Distributed Denial of Service (DDoS) attack.

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Having a third party with access to your inbox data increase the attack surface present to hackers and other people wanting access to my stuff.

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Firewalls and AV programs are completely ineffective against state-sponsored attacks because adversaries who are targeting high value data have multiple attack vectors to choose from that would be utterly invisible to automated defenses.

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