How long should a Security Engineer cover letter be?

Three to four short paragraphs, roughly 300–400 words, on no more than one page. Longer letters typically go unread.

What should a Security Engineer cover letter include?

Open with a quantified achievement related to finding and closing vulnerabilities, match the posting's key requirements (such as application security and penetration testing) with things you actually did, name one specific reason you want this company, and close briefly.

Do cover letters get scanned by an ATS?

Some applicant tracking systems parse cover letters as well as resumes, so include relevant keywords naturally — but never pad with skills you don't have.

Security Engineer cover letter example

Short answer

A strong Security Engineer cover letter is 3–4 short paragraphs, roughly 300–400 words, and answers two questions: what you can deliver (for this role, that means finding and closing vulnerabilities) and why this company. Open with a quantified achievement rather than "I am writing to apply", name the skills the posting asks for (application security, penetration testing), and include one specific detail about the employer.

Full example

Replace the bracketed parts with your real details.

Dear Hiring Manager,

I'm applying for the Security Engineer role at [Company]. Over the past [X] years I've
focused on finding and closing vulnerabilities, most recently [one concrete achievement with a
number — %, revenue, users, time saved].

Your posting emphasises application security and penetration testing. At [Current Company] I [what you did
with those skills], which [quantified result]. I work with application security, penetration testing, SIEM
day to day, and I'm comfortable responding to security incidents.

What draws me to [Company] is [one specific product, initiative or value —
this is the line that shows you didn't mass-send this letter]. I'd like to
bring my experience in finding and closing vulnerabilities to your team.

Thank you for your time — I'd welcome the chance to talk further.

Sincerely,
[Your name]

Short version (for application forms)

When the form gives you a small text box or asks for a note to the hiring manager:

Dear [Name],

I'm a Security Engineer with [X] years in finding and closing vulnerabilities. At [Company] I [achievement
with a number].

Your posting calls for application security and penetration testing — both are core to my day-to-day work.
I'd love to bring that to [Company], particularly given [specific detail
about the company].

Happy to share more. Thank you for your time.

[Your name]

Paragraph by paragraph

Opening

Name the role, then immediately give a result tied to finding and closing vulnerabilities. Skip "I am writing to apply for…" — it wastes your strongest line.

Proof

Take the one or two requirements the posting leads with (usually application security and penetration testing) and match each with something you actually did, with a number attached.

Why this company

One specific product, launch, or value. This is what separates a targeted letter from a template.

Close

One or two lines. Thank them, signal availability, stop.

Keywords to work in naturally

Some employers scan cover letters too. Include the ones you genuinely have — never pad.

application securitypenetration testingSIEMvulnerability managementOWASPIAMencryptionincident responsePythoncloud security

Five mistakes to avoid

✕ Restating the resume

The letter should add what the resume can't show: motivation, judgement, and why this company.

✕ Mass-sending one letter

If nothing in the letter names the company or its work, recruiters can tell instantly.

✕ Leading with what you want

Lead with what you can deliver. Your goals come second.

✕ Going over one page

300–400 words is the sweet spot. Longer letters mostly go unread.

✕ "To Whom It May Concern"

Find the hiring manager on LinkedIn. If you truly can't, "Dear Hiring Manager" is fine.

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