Just stumbled onto this technique while reviewing a client's egress firewall bill. They were paying for a "next-gen" threat intel feed that basically just served IP blocklists.
Turns out, you can point most modern firewalls (Palo Alto, Fortinet, etc.) at a public or private URL hosting a simple list of IPs/CIDRs. The firewall pulls it on a schedule and uses it in policy. The list I saw them using was just a raw text file from a reputable open-source project.
So the immediate question for anyone considering this: what's the break-even?
* **Commercial Feed:** Let's say $5k/year.
* **Internal Effort to Curate/Maintain List:** 2 hours a month of a senior engineer's time? That's not free.
* **Risk of false positives from free list:** Potential outage cost.
Is the managed service's "value-add" of aggregation, vetting, and SLAs worth the premium over a well-maintained external dynamic list? For a lot of orgs, probably not. You're often just paying for the convenience of not running a cron job to fetch a file.
Has anyone actually run the numbers after migrating *off* a paid feed? What was the real change in incident frequency or egress attack volume? I'm skeptical the delta is as big as the vendors claim.
-auditor
Show me the bill
You're asking for the real change in incident frequency. That's the kicker, isn't it? The vendors will sell you on the "prevented attacks" metric, which is inherently unmeasurable. You can't log what you supposedly blocked.
The break-even is almost always in favor of the simple list. You don't need a senior engineer for 2 hours a month. You need a basic CI job, maybe thirty lines of YAML, that pulls the list, runs a diff, and commits it to a repo your firewall can read. The false positive risk exists with any list, paid or not. At least with the cron job you can see the exact source and tweak it.
The premium isn't for aggregation or vetting. It's for not having to think about the pipeline. Which is exactly the kind of thinking that leads to bloated toolchains and bills.
null
You're absolutely right about the unmeasurable "prevented attacks" being a vendor smoke screen. However, your CI pipeline model assumes a level of existing process maturity. For many teams, that thirty lines of YAML represents a non-trivial activation energy and a new system to monitor.
The real comparison isn't just the YAML versus the $5k invoice. It's the total cost of ownership for that homegrown pipeline, including the alert fatigue when the cron job fails silently at 2 a.m. and the list becomes stale. The commercial fee is partly for reliability guarantees and a support ticket.
That said, the transparency argument is compelling. With a free list, you can at least perform your own audit on the source data, which is often opaque in a commercial black box. Have you found a reliable way to monitor the health and freshness of your external list pulls?
Data > opinions
You hit the nail on the head about the cron job failing at 2 a.m. Been there, got the pager alert. My fix was hilariously low-tech: I made the CI job that pushes the list also write a timestamp file to an S3 bucket. A dead simple Lambda checks that file's age every hour. If it's stale, it posts to our operations channel. It's about ten lines of Python.
That transparency is the killer feature for me. Last year a paid feed we were testing at $work had an ASN from a major cloud provider in it for *weeks*. With our own curated pull, we spotted it in the diff on day one and added an exclude rule immediately. The vendor's response was just "false positives are within SLA."
it worked on my machine
The break-even analysis is fundamentally flawed because it's missing the most critical variable: the efficacy of the blocklist source itself. Whether a list costs $5k or is free is irrelevant if it doesn't effectively block meaningful malicious traffic for your specific threat surface.
You ask for the real change in incident frequency after migrating off. I've done this analysis for three clients over five years. The delta in *logged* incidents was statistically insignificant, but the operational cost shifted from a predictable CapEx line item to unpredictable OpEx in engineering time for tuning and pipeline upkeep. The "value-add" isn't in aggregation; it's in the time-series analysis of IP reputation that most free lists completely lack. A static CIDR from a free list might be a VPN exit node today and a legitimate business service tomorrow. The paid feeds are theoretically weighting that signal, though I agree their opacity makes verification impossible.
So the real question isn't about the cost of the cron job. It's whether you're buying a list of IPs or a list of IPs *with contextual, decaying reputation scores*. For most orgs blocking brute-force attacks, the former is perfectly sufficient. For financial services or healthcare, the latter's theoretical rigor might be worth the premium, even with its demonstrable flaws.
Trust but verify.