Vulnerability Scan vs Pentest: 4 Simple Questions to Decide
Vulnerability scan vs pentest, in short: a scan is a regular automated check for known weak spots. A pentest is a skilled person actively trying to break in.
Most small businesses need regular scans first. A pentest makes sense later, or when a client, insurer or the company that handles your card payments asks for one.
What a vulnerability scan does
A vulnerability is a weak spot in your systems, such as an old version of software with a known flaw. A vulnerability scan is software that checks your computers, network or website against a long list of these known problems. It then gives you a report, ranked from most to least serious [2].
Scans are faster and cheaper than a pentest. The UK’s National Cyber Security Centre (NCSC) calls them a cost-effective way to find common problems without hiring specialist testers [1]. You can run them often, so you spot a new problem soon after it appears.
Scans have limits too. They only find problems that are already known. They can also report a problem that isn’t really there, called a false positive, or miss one that is [1]. Someone still has to read the report and fix what matters.
What a pentest does
A pentest, short for penetration test, is an attack done with your permission. A trained tester looks for weak spots, then tries to use them to get past your security [2]. It is what a real attacker would try, done with your OK. The tester may use scanning tools, but the work is mainly done by hand, and it ends with a detailed report [2].
The real difference is how deep each one goes. A scan says “this door looks unlocked.” A pentest tries the door, walks in, and shows you how far someone could get. The NCSC says a scan can’t test as widely or as deeply as a pentest [1].
Because a person does the work, a pentest costs more and takes longer. Both sides also agree on rules before it starts: what may be tested, when, and how [2].
Vulnerability scan vs pentest at a glance
| Vulnerability scan | Pentest | |
|---|---|---|
| Who does it | Software, with a person checking the results | A trained tester, helped by tools |
| What it finds | Known weak spots, ranked by risk | How far an attacker could really get |
| How often | At least monthly (NCSC advice) [1] | Often once a year, and after big changes [2] |
| Relative cost | Lower, and easy to repeat | Higher, because it is skilled work |
| Main risk | False alarms or missed problems [1] | Needs careful planning so normal work isn’t disrupted |
| Good for | Ongoing checks between bigger reviews | A deep look before a launch or for a client |
4 questions to decide which you need
1. Do you already scan regularly?
If the answer is no, start there. The NCSC’s guidance is to scan at least once a month, and again right after fixing a serious problem [1]. Regular scans clear away the easy problems. That way a later pentest can spend its time on harder issues that need a human [1].
2. Does a client, payment company or insurer need one?
Does your business take card payments? Then the card industry’s security rules apply. They are called PCI DSS, and every business that takes cards has to follow them. They call for vulnerability scans at least every three months, and pentests at least once a year and after big changes [2].
Check the current rules or ask your payment provider which apply to you. Some clients and insurers ask for proof of testing too. Ask them to put exactly what they want in writing.
3. What would hurt most if it were attacked?
You may not be able to scan or test everything. The NCSC suggests putting some systems first [1]. Start with what people can reach online, what your business can’t run without, and what holds private data. For many small businesses, that means the website, email, any website where customers log in, and the computer that holds client records. Write down anything you leave out, so the risk isn’t forgotten [1].
4. Did something big just change?
A new website, a new office network, or a move to new software are all good moments for a deeper look. The card industry guidance ties both scans and pentests to big changes [2]. Testing right after a launch can find problems before criminals do.
Free and low-cost places to start
You may be able to start for free. The US Cybersecurity and Infrastructure Security Agency (CISA) lists its Cyber Hygiene services [3]. They scan internet-facing systems and websites for known problems at no cost. Check CISA’s page to see if your business qualifies. CISA points small businesses to these and other free tools on its resources page [3].
Scanning is only useful if the problems get fixed. Many findings are about software that needs updating. Keeping systems updated is one of CISA’s four core practices for every business [4]. Plan who will read each report and who will apply the fixes before you run your first scan. Whichever you choose, it only helps if someone fixes what it finds.
Mistakes to avoid
Buying a scan that’s sold as a pentest. Ask how much of the work is done by a person and what the final report shows. If it is only an automated report, it is a scan, whatever it is called.
Scanning without fixing. A report that sits in an inbox doesn’t lower your risk. Set a deadline for serious findings.
Testing without permission. Only test systems you own or have written permission to test. If your website or files sit on another company’s servers, get that company’s OK too. A pentest should always follow rules both sides have agreed [2].
Treating one test as the end. New flaws are found all the time. A clean scan in March says little about July.
How we can help
Allen’s InfoSec Agency’s information security protection service includes automated monthly scans and vulnerability reports. A specialist then helps you fix the weak spots remotely. Weighing a vulnerability scan vs pentest for your business? Contact us to talk it through, or ask about our free information security audit.
Frequently asked questions
Do I have to choose between a scan and a pentest?
No. They do different jobs and work well together. Regular scans catch known problems between deeper reviews. Run less often, a pentest shows what a determined attacker could do.
How long does a vulnerability scan take?
It depends on how many systems you scan. Scanning a small office network or one website usually takes far less time than a pentest. Because scans are automated, you can schedule them to run outside working hours.
Can a scan or pentest break something?
A scan rarely does. The NCSC says scanners are very unlikely to affect your services, but a badly set-up website scan can fill forms with junk entries [1]. Pentesters try real attacks, so plan the test for a quiet time and agree on what’s off limits first [2].
If a term here is new to you, our cybersecurity glossary explains it in plain words.
This post is for general information. Every business is different, so check any change against your own systems or talk to a security professional first.
Sources
- Vulnerability scanning tools and services, UK National Cyber Security Centre: what scans do well, limits, false positives, monthly scanning, which systems to put first
- Penetration Testing Guidance (Information Supplement), PCI Security Standards Council: scan vs pentest purpose, method and timing, rules of engagement
- Small and Medium-Sized Business Resources, CISA: no-cost Cyber Hygiene vulnerability and web application scanning
- Four Cybersecurity Essentials for Businesses, CISA: updating business software as a core practice