Cybersecurity Audit of Top Illinois Accounting Firms in 2026

An independent cybersecurity review across many of Illinois’s largest accounting firms reveals a wide range of results. Firms that prepare returns hold extremely sensitive taxpayer data, yet many show significant gaps in basic email authentication.

Using data from audit.emailmenow.com, we evaluated each firm’s domain across SPF, DKIM, DMARC, transport security (MTA-STS/TLS), and website security headers.

Cybersecurity Scores of Major Illinois Accounting Firms

Overall compliance scores from audit.emailmenow.com. Re-run any domain at the link to verify.

Website Security Scores

Scores ranged from 92% to 45%; 0 of 10 reached the 100% ideal and 7 scored below 60%.

What the Results Reveal

• Illinois leads our accounting-firm reviews: four firms clear 70%, topped by Plante Moran and Selden Fox at 84%.
• Even so, none reach 85%, and the field tails off to 49% — enforced DMARC, strict SPF, and transport protections aren’t universal even among the leaders.
• Weak email authentication fuels the tax-season phishing and client-payment fraud that increasingly target CPA firms.

Attack exposure in this audit

Domains scoring near 45% combine weak identity enforcement, missing inbound transport protections, and sub-60% website hardening. Without naming specific organizations, entities in that tier are disproportionately exposed to:

• Business email compromise (BEC) — spoofed messages appearing to come from executives or accounts payable, used to redirect wires and ACH payments.
• Brand impersonation phishing — fake billing, HR, and vendor notices that pass visual inspection because DMARC and SPF are not fully enforced.
• Credential harvesting — login pages linked from forged @company.com mail aimed at employees, contractors, and customers.
• Invoice and procurement fraud — altered payment instructions sent to finance teams and partners who trust the corporate domain.
• Account-recovery abuse — password-reset and MFA prompts triggered from impersonated sender addresses.
• Inbound mail downgrade attacks — absence of enforced MTA-STS allows opportunistic TLS stripping on messages destined for the organization.
• Clickjacking and session risks — missing HSTS, CSP, and frame protections on the public site increase browser-side attack surface for visitors and logged-in users.
• Supply-chain targeting — partners who whitelist the domain for deliverability become secondary victims when spoofed mail originates unchecked.

These are not theoretical edge cases. State breach portals and FBI IC3 reporting consistently tie weak email authentication and header gaps to measurable financial loss at large enterprises.

Real attacks, told as stories

The stories below are made up, but they are based on real crimes that police and cybersecurity teams see every year. No Illinois accounting firm is named. Each story shows how weak domain settings can hurt real people — customers, partners, and staff who work with Illinois accounting firms.

Story 1: Maria and the payment that was not real

Maria works in accounts payable at Midwest Parts, a supplier that has sold to a big national brand for ten years.

On a Tuesday morning, she gets an email that looks normal:

From: accounts-payable@bigbrand.com
Subject: New bank info for March invoices

The logo looks right. The tone sounds like past emails. A PDF lists a new routing number.

Maria does not know that bigbrand.com has weak email security. A stranger sent the message from their own server and pretended to be the big brand. That is called brand impersonation.

She approves a $284,000 wire. The money goes to the attacker, not the real company.

The next day, the same fake sender emails two more partners Maria knows from trade shows. One ignores it. One also changes bank details. That is supply-chain targeting — hurting partners by faking the main organization’s name.

Attack vectors in this story: brand impersonation · invoice and procurement fraud · supply-chain targeting · business email compromise (BEC)

Simple fix: Strict DMARC (p=reject), SPF (-all), and a rule that every bank change needs a phone call to a known contact — not just email.

Story 2: Jordan clicks “reset password”

Jordan is a facilities manager at a large tech company. On Wednesday at 2 p.m., his phone buzzes:

From: it-security@bigbrand.com
Subject: Reset your password in 2 hours or lose access

Jordan is busy. The email looks like IT mail he has seen before. He clicks the link.

The page looks like his company login. It is not. It is a copy on a similar-looking website (bigbrand-secure.com). He types his username and password. The attacker saves them.

This is account-recovery abuse and credential harvesting. The criminal used a fake “reset your account” message because people trust mail from @company.com.

That night, the attacker signs into Jordan’s mailbox and reads old threads about a possible acquisition. On Thursday, they email the CFO’s assistant:

From: cfo@bigbrand.com
Subject: Urgent — confidential wire for escrow

That is BEC — business email compromise. The assistant almost approves it. A bookkeeper asks, “Did you talk to the CFO on the phone?” The wire stops. Jordan still has to change every password he reused.

Attack vectors in this story: account-recovery abuse · credential harvesting · business email compromise (BEC)

Simple fix: DMARC p=reject, train staff that IT will never rush a reset by email alone, and require a callback before any wire.

Story 3: The contract email no one knew could be copied

Priya is a lawyer at the same big brand. She emails a draft contract to an inbox at @bigbrand.com. The send button works. Her screen says Delivered.

What Priya cannot see: on part of the internet path, the mail server connection was downgraded from locked (TLS) to unlocked. Without MTA-STS set to mode=enforce, the recipient’s mail system still accepts the message. An attacker on that path can copy attachment text in plain form.

This is an inbound mail downgrade attack. Most people worry about fake outgoing email. MTA-STS protects incoming mail — mail sent to your organization.

Priya’s IT team sees green checkmarks in their dashboard. Nothing looks wrong. Weeks later, a competitor seems to know bid details early. The leak might have started on the wire, not in someone’s inbox.

Attack vector in this story: inbound mail downgrade (no MTA-STS)

Simple fix: Publish MTA-STS in enforce mode and turn on TLS-RPT reports so IT gets alerted when encryption fails.

Story 4: Alex applies for a job online

Alex is a college senior. He is already logged into his school portal in one browser tab. In another tab, he opens a job post: “Big Brand — analyst role, fast track.”

The site asks him to “confirm your profile” on what looks like the real company careers page. He clicks.

He does not know the page is a trap. The real login screen is hidden inside an invisible frame on a scam site. That trick is called clickjacking. The company’s website scored 45% on security headers, missing strong HSTS, CSP, and frame blocking.

Alex thinks he is on the real site. He is really interacting with a layer the attacker controls. If he had been logged into the company’s vendor portal in another tab, the same trick could hijack that session.

No phishing email was needed. The attack lived on the website, not in the inbox.

Attack vectors in this story: clickjacking · session risks (missing HSTS/CSP)

Simple fix: Add HSTS, Content-Security-Policy, and frame-ancestors / X-Frame-Options so login pages cannot be embedded on random sites.

How the stories connect

All four stories can hit one organization with a weak audit score (near 45%):

Together, that is not one bug — it is a pattern. Fixing it means better DNS (DMARC, MTA-STS), better website headers, and better office rules (call back before you wire).

Why This Matters for Accounting Firms

The IRS (Publication 4557) requires every tax professional to maintain a written information security plan (WISP) to keep a PTIN, and the FTC Safeguards Rule backs it with civil penalties. Tax season is also peak phishing season for tax pros.

Check any firm’s posture at audit.emailmenow.com/?industry=cpa-firms&state=illinois.

See also — national audit

• Major U.S. CPA Firms (national)
• Major U.S. Tax Preparers (national)
• National Payroll Providers (national)

Recommendations

• Enforce DMARC (p=reject), strict SPF (-all), and DKIM signing.
• Add MTA-STS and website security headers.
• Document your WISP and run recurring security awareness training before filing season.

Protect your firm and your clients. Run a free Instant Cybersecurity Audit at audit.emailmenow.com/?industry=cpa-firms&state=illinois.

Contact EmailMeNow IT Consulting for help with your IRS-ready written security plan and email hardening.

Source & methodology: Overall compliance scores from the free scan at audit.emailmenow.com — each domain checked for email authentication (SPF, DKIM, DMARC), transport security (MTA-STS/TLS), website security headers, and network security. Re-run any domain at the link to verify.