Am I being (D)DoS'd?

This is a great question! The answer here, I'm afraid, might not be as conclusive as you'd like: it depends. Identifying (D)DoS attacks can be pretty confusing because it can be hard to tell whether or not a spike in traffic is due to legitimate users querying your site. That being the case, it's good practice to keep track of your Linode's normal activity so that it's easier to tell when something is amiss -- strange activity might mean requests from IP addresses that should have no reason to contact your Linode, or sources that continue to make requests for certain data after the TTL has expired.

What can I do to protect myself against (D)DoS attacks?

Due to the difficulty of accurately spotting legitimately malicious activity, we often recommend taking preemptive measures to guard your Linode (an ounce of prevention is worth a pound of cure!). This would include the following:

• Hiding your Linode behind a CDN such as Cloudflare
• Efficiently configuring your Linode's firewall rules
• Using intrusion prevention software such as fail2ban
• Sizing your Linode so that normal activity doesn't impact its performance

If anyone else here has any other suggestions, I'd encourage you to share them below. Thanks in advance!