Many of today’s breaches do not start with clever malware. They start with someone logging in. This month, Japanese media group Nikkei disclosed its third security incident in about a month: attackers used stolen credentials to reach a development system and exposed about 1.83 million records, around 150,000 of which contained personal details such as names and email addresses. Earlier incidents at the same company involved a hijacked Google Workspace account and a compromised Microsoft 365 account that was used to send spear-phishing emails to staff.

Small businesses use exactly the same platforms, often with default settings left untouched. The good news is that both Microsoft 365 and Google Workspace include strong protections, and most can be switched on by an administrator in an afternoon. This guide walks through the most important steps. You will need an account with administrator rights.

Step 1: Protect the admin accounts first

An attacker who controls an administrator account controls everything, so start here.

1. Use separate admin accounts. Give administrators a dedicated admin login that is not used for daily email or browsing.
2. Keep the number small. Two administrators is usually enough for a small business: one main and one backup, so you are never locked out.
3. Turn on the strongest sign-in method available for those accounts, such as a hardware security key or an authenticator app, before anything else.
4. Store a break-glass account securely: an emergency admin login, with its recovery details written down and kept offline.

Step 2: Enforce multi-factor authentication for everyone

Multi-factor authentication (MFA) means a stolen password alone is not enough to sign in. The key word is enforce: offering MFA as optional leaves gaps.

In Microsoft 365

1. Sign in to the Microsoft Entra admin center (entra.microsoft.com).
2. If you do not have advanced licences, make sure Security defaults are enabled. They require all users to register for MFA and block older, weaker sign-in methods.
3. If your plan includes Conditional Access, create a policy that requires MFA for all users and all cloud apps, and test it on a small group first.

In Google Workspace

1. Sign in to the Google Admin console (admin.google.com).
2. Go to Security, then the 2-Step Verification settings.
3. Allow users to turn on 2-Step Verification, give staff a short enrolment period, and then set enforcement to on.
4. Where possible, restrict methods to security keys or the Google prompt rather than SMS codes.

Tell staff before you enforce MFA, and set a date. A short notice prevents a Monday morning full of lockouts.

Step 3: Close the side doors

Attackers often bypass MFA through older protocols or connected apps.

• Block legacy authentication. Older email protocols such as POP, IMAP and basic SMTP authentication may not support MFA. In Microsoft 365, Security defaults or a Conditional Access policy can block them. In Google Workspace, review the settings for less secure app access and IMAP for users who do not need them.
• Review third-party app access. Staff may have granted outside apps permission to read mail or files. In Microsoft Entra, review Enterprise applications and consider requiring admin approval for new app consents. In the Google Admin console, open Security > Access and data control > API controls to see and restrict connected apps.
• Stop automatic forwarding. Criminals who take over a mailbox often set a rule to copy all mail to an outside address. Disable automatic external forwarding unless there is a business need.

Step 4: Turn on alerts and check sign-in logs

You want to know quickly when something looks wrong.

1. In Microsoft 365, review sign-in logs in the Entra admin center and alert policies in the Microsoft Defender portal (security.microsoft.com). Look for sign-ins from unexpected countries and new inbox rules.
2. In Google Workspace, use Reporting > Audit and investigation for login events, and check Rules for alerts such as suspicious login and user granted admin privilege.
3. Send alerts to a shared mailbox that more than one person checks.
4. Set a recurring 15-minute weekly slot to skim the logs. Regular, small checks catch problems early.

Step 5: Plan for the day a login is stolen

Even with good controls, an account may be compromised. Prepare the response in advance:

• Know how to reset a password and sign the user out of all sessions in your admin console.
• Know how to revoke app tokens and remove suspicious inbox rules.
• Write a one-page checklist listing who to call, including your IT provider and bank, if a mailbox is used for fraud.
• Remove accounts promptly when staff leave, and transfer their data to a manager.

Quick checklist

• Separate, protected admin accounts, kept to a minimum
• MFA enforced for every user, not just offered
• Legacy sign-in blocked and external forwarding disabled
• Third-party app access reviewed
• Alerts on and logs checked weekly
• A written plan for a compromised account

Menu names change from time to time as Microsoft and Google update their consoles, so if a setting has moved, search for it by name inside the admin portal. The steps themselves remain among the most effective defences a small business can put in place.

Sources

• BleepingComputer: Nikkei discloses third data breach in a month, 1.8M records exposed

Featured image: Photo: “UF Norman Office Laptop Desk Workstation” by cdsessums, CC BY 2.0, via Openverse — source