Form spam: a practical guide

There is no clever trick in this one, just a handful of decisions worth making deliberately. This guide covers what form spam actually involves, where it usually goes wrong, and how to tell whether yours is in reasonable shape.

The cheapest security work is the boring kind done on a schedule. Nothing below assumes a large team or a large budget — most of it is a decision somebody has to make and then write down.

Why it matters

Honeypots stop most bots without troubling humans. The reasoning matters more than the rule, because the rule has exceptions. Check it against what you would want a competitor's site to get wrong.

For most businesses the question is not whether this matters but how much of it is worth doing right now. That depends on what you are trying to achieve in the next few months, not on best practice in the abstract. There is a version of this that is over-engineered, and it is worth avoiding.

How we handle it

CAPTCHAs cost real conversions. The reasoning matters more than the rule, because the rule has exceptions. Anything you cannot measure here, you are deciding by taste, which is fine as long as everyone knows it.

The realistic threat for most small businesses is automated and opportunistic, not targeted. The version that works in practice is usually less elaborate than the version described in the guides.

Rate limiting handles the rest. The teams that handle this well are rarely the ones with the biggest budgets. Assume whoever inherits this will have half your context and none of your patience.

A working checklist

If you want a quick read on where you stand, work through this. Anything you cannot answer confidently is where to start.

• Honeypots stop most bots without troubling humans
• CAPTCHAs cost real conversions
• Rate limiting handles the rest
• Someone is named as the owner, not just assumed to be
• There is a date in the calendar to review it again
• The decision and the reasoning behind it are written down somewhere findable
• You could explain the current setup to a new hire in five minutes

Common failure modes

The most common failure is not doing this badly. It is doing it once, during a launch, and never revisiting it. Circumstances move, the setup does not, and the gap widens quietly until something breaks or somebody notices the numbers.

• It was configured during a launch and has not been touched since
• Different people in the business believe different things are true about it
• There is no way to tell whether the last change helped or hurt
• The only person who understands it has left, or is about to

Security is a maintenance habit rather than a purchase, which is why it drifts. There is a version of this that is over-engineered, and it is worth avoiding.

How we approach it

On our projects this gets handled during the build rather than added afterwards, because retrofitting it costs several times more than including it. We write down what was decided and why, so the next person to touch it is not guessing.

If you are working with someone else, the questions worth asking are simple: who owns this, how will we know it is working, and what happens when it needs to change?

Where to go from here

Pick the single item from the checklist above that would cause the most trouble if it turned out to be wrong. Fix that one, confirm it worked, then move on. Worth checking on your own setup before it becomes someone else's problem to fix.