Email is still one of the most common ways attackers get in. Phishing, credential theft, impersonation, and business email compromise (BEC) all start with a message that looks like it belongs. For an MSP, the stakes are higher. A single compromised mailbox can expose your own business, and it can also give an attacker a trusted voice to use against your customers.

Email security measures work in layers:

• Email authentication. SPF, DKIM, and DMARC verify that a message really comes from the domain it claims. They make it harder for attackers to spoof your domain or your customers' domains, and they give receiving servers a way to reject fakes. Configure and monitor them for your own domains and for every customer domain you manage.

• Inbound filtering. Spam, malware, and phishing filters screen messages before they reach an inbox. Modern filtering goes beyond sender reputation to catch lures that older rule sets miss.

• Advanced threat protection. Sandboxing attachments and checking links when they're clicked, not just when the email arrives, helps catch malicious content that looks clean on delivery.

• Outbound filtering. Scanning outgoing mail can catch sensitive data leaving the organization, and it can reveal that an internal account has been compromised and is being used to phish others.

Filtering has limits, though. Many BEC attacks contain no malware and no malicious link, just a convincing request from someone who seems trustworthy, such as a vendor asking to change payment details or an "executive" asking for an urgent transfer. Others succeed after the message is delivered, when a user enters credentials on a fake login page or approves a malicious app. Once an attacker is in a mailbox, they might set up forwarding rules, hijack reply threads, or hide their tracks.

That's why email security works best alongside the identity layers in this stack.

Email security can certainly help block some phishing emails before they reach recipients, but some messages still get through. In these incidents, security awareness training can help targeted employees better understand the major red flags, like urgent language or strange requests. The 2025 Huntress Cyber Threat Report found that threat actors are upping their phishing game with techniques like QR code phishing, image-based content, and brand impersonation. Security awareness training can help employees identify these types of social engineering threats, as well as attacks that go beyond email-based phishing, like deepfakes or scams.

Threat actors are increasingly using identity-based techniques to target organizations. E.g., compromising employees' passwords and then using that access as a stealthy launch point for further attacks. This is made easier for  threat actors when people reuse passwords or create easy-to-guess passwords, opening the door for brute force attacks, credential stuffing, and more. Password managers can help users automatically generate new, unique passwords for each site. They can also help users store and manage these credentials so they don't have to remember them, reducing the risk of password reuse.

If threat actors do manage to steal employee credentials, MFA is an important preventative measure to stop them in their tracks. MFA involves two or more forms of authentication beyond a password, whether that's a push-based authentication app or a biometric fingerprint scan. MSPs should enable MFA on accounts, services, and applications as a baseline security measure.

MSPs should have patch management tools and procedures in place to make a comprehensive game plan for the process of finding, testing, and deploying fixes for security vulnerabilities. That’s because one way threat actors find their way into an organization is by exploiting vulnerabilities. Many times, these flaws have previously been found and fixed by the product manufacturers, but MSPs don’t make the actual update to the software version that patches the flaws, leaving a gaping hole open to attackers. A patch management plan can help MSPs ensure that critical-priority fixes and patches for flaws being exploited by attackers don’t fall through the cracks.

IAM is a framework of policies and procedures that helps businesses manage user access to systems and resources. Through this framework, IT administrators can restrict access across resources to make sure that the right individuals have the right level of access. This can help prevent unauthorized access.

While IAM focuses on access policies, ITDR focuses on incidents where those access controls are bypassed by detecting and responding to suspicious identity threat behavior. Identity-related threat behavior includes unauthorized access, the misuse of credentials, and more. ITDR solutions typically involve real-time threat detection for suspicious behavior, monitoring for attack techniques, and automated remediation to stop identity attacks. MSPs can use ITDR to protect themselves against credential theft, account takeover, business email compromise, and session hijacking.

Detection catches attacks in progress. Posture management reduces the chances they succeed. Identity posture management continuously checks your Microsoft 365 and Google Workspace environments for weaknesses attackers rely on, such as missing MFA, legacy authentication, overly broad admin roles, and risky configuration drift. For MSPs, this matters twice: once for your own tenant, and again across every customer tenant you manage. Pair it with ITDR so you can both harden identities and respond when something still gets through.

EDR is another important tool for MSPs to have in their arsenal. EDR focuses on protecting endpoint devices by monitoring for and finding potentially suspicious activity. EDR provides MSPs with the ability to proactively detect and remediate against threats on endpoints while they happen. While many of the other practices and tools that we’ve outlined thus far have focused on keeping threat actors out from the start, EDR focuses on the incidents where attackers have still managed to slip through the cracks and stops the attack before it can escalate.

Endpoints drift. Protections get disabled, configurations fall out of baseline, and security settings vary from device to device. Endpoint posture management helps you find and fix those gaps before an attacker does, so your EDR is working from a stronger starting point. Together, posture management reduces your attack surface, and EDR catches what remains. 

Antivirus is still a useful prevention layer. It blocks known malware like viruses and ransomware before it can run, and for most Windows environments, Microsoft Defender Antivirus is already built in. But antivirus alone doesn't investigate suspicious activity, hunt for attackers who've already gotten in, or respond when something slips through.

That's why antivirus works best paired with EDR. Defender provides the prevention layer, and Huntress Managed EDR adds endpoint telemetry, detection of attacker behavior, and a 24/7 SOC that investigates and responds.

For MSPs, the pairing also solves an operational problem. Defender is only as good as its configuration, and settings, exclusions, and protections tend to drift across dozens of customer environments. With Managed Microsoft Defender, Huntress centrally manages supported Defender Antivirus configurations, exclusions, scans, and detections across tenants from one platform, and it's included with Managed EDR on supported Windows endpoints. You also get visibility into Defender health, policy compliance, tamper-protection status, and risky exclusions.

Huntress then layers on detection Defender doesn't provide as a managed service, such as Persistent Footholds detection and Ransomware Canaries. If you already use Defender for Business or Defender for Endpoint, Huntress can also ingest that telemetry to give the SOC a fuller picture. In short, Microsoft builds the controls, and Huntress runs them.

Most of the tools above watch one control point: an endpoint, an inbox, or an identity. But attacks rarely stay in one place. An attacker might log in with stolen credentials, touch a VPN or firewall, move to a server, and then reach a customer environment. Each step leaves a trace in a different log. SIEM is how you pull those traces together.

A SIEM collects logs and security events from across your environment, including endpoints, firewalls, VPNs, identity systems, and cloud platforms, and centralizes them so you can search and analyze activity in one place. For an MSP, that gives you three things:

1. Earlier detection with more context. Correlating events across sources can surface initial access, lateral movement, and data exfiltration that endpoint telemetry alone might not show.

2. Faster, better investigations. When an account or management tool may be compromised, centralized, searchable logs let you answer "what happened, and what else did it touch?" without piecing together evidence from separate consoles. This is especially important if you need to show a customer exactly what was and wasn't affected.

3. Compliance evidence. Auditors, regulators, and cyber insurers increasingly expect security events to be recorded, retained, and searchable. SIEM gives you that record, and you can use it to support your own compliance needs and those of customers in regulated industries.

SIEM also has a reputation for being expensive, noisy, and hard to run. Traditional deployments ingest everything, which drives up storage costs, buries real signals in false positives, and demands skilled staff to tune and monitor them. Most MSPs don't have a spare SIEM engineer, so how a SIEM is delivered matters as much as whether you have one.

Huntress Managed SIEM is built for that reality. Smart Filtering keeps security-relevant events rather than every log line, which reduces noise and storage costs. The Huntress 24/7 SOC writes and tunes detections, investigates suspicious activity, and escalates confirmed incidents with clear next steps, so you don't have to staff or tune it yourself. Data can be retained for up to seven years to support compliance requirements, and pricing is by data source with a pooled data allocation to avoid billing spikes.

SIEM and EDR work best together. EDR shows you what's happening on a specific machine right now, while SIEM shows you what's been happening across the environment over time. When one SOC watches both, each fills in context the other lacks.

A practical way to start: turn it on in your own environment first, then expand to a small group of customers and scale from there. Your own logs are where a compromised account or RMM tool would show up first.

MSPs reading this list may feel overwhelmed by the different practices, solutions, and frameworks needed to build out their security stack. You don't need every layer on day one, and no single tool covers them all. Attackers target endpoints, identities, email, and the management tools MSPs use to reach customers, so the goal is a stack in which one compromised account or device can't take down everything else.

If you're deciding where to start, work in this order:

1. Lock down identity. Enforce phishing-resistant MFA, limit privileged access, and harden your Microsoft 365 environment with identity posture management and ITDR.

2. Secure and monitor endpoints. Pair managed EDR with Defender and endpoint posture management so protections stay configured and threats get investigated.

3. Protect your management tools. Secure your RMM, separate customer access, and keep patching on a risk-based schedule.

4. Build visibility and recovery. Centralize and retain logs with SIEM, agree on incident response roles with customers, and test your backups.

Whatever you add, protect your own business first. A compromised MSP puts every customer at risk, so your internal stack deserves the same layers you'd recommend to them.