Many security incidents begin in email: a simple message can trigger ransomware, data theft, or a financial scam. The good news is that with practical training and simple checks, most attempts can be stopped. before it's too late.
In this guide, I explain in detail and with real-life examples how to recognize and handle dangerous emails, what to do if you have any doubts, how to respond if you've already clicked, and what tools you should activate. Integrate habits, technical controls and processes so that email is no longer the weak link both on a personal level and in your company.
Clear signs to detect malicious emails
Before reading the message, look at where it comes from. The sender's address is your first clueIf you don't know the person, examine the domain closely. Look for minor typos, missing letters, or domains that mimic brands (e.g., banco-santander instead of the real domain). Many attackers use meaningless strings of letters and numbers or screen names that don't match the real address.
Analyze the subject line. Typical lures use urgency or alarm: suspicious activity, prize, pending invoice, immediate verification. Its goal is to get you to open it and click without thinking. If you weren't expecting that message, raise your eyebrow and apply the rest of the checks.
Review the content calmly. Grammatical errors, awkward translations, unnatural tone, or generic formulas Without personalization, such as "Hello" in supposedly important messages are common indicators. Note: There are increasingly polished campaigns, so don't rely solely on spelling.
Rate the level of detail. Frauds are usually vague and without concrete references. to services, orders, or mutual contacts. If you receive a message from a company, check out their website on Google yourself and compare whether the content matches what they claim to sell.
Check links without clicking. Hover to see the actual URL or tap and hold on mobileIf it doesn't match the legitimate domain, if it's shortened to hide it, or if it sounds odd, don't go there. You can copy the URL (right-click, copy) and analyze it with services like VirusTotal, Sucuri, or URLVoid.
Be careful with attachments. An invoice, a resume or a report can carry the malicious payload. Be wary of generic names, requests for enable macros in Office or unusual formats. Compare the nomenclature with previous documents if you're a regular supplier.
Signature and coherence. If the signature does not match the sender or corporate data is missing, a bad sign. And if the email boasts of legitimacy with brands, seals, or high-value priorities to pressure you, remember that these are widely used false legitimizers.
Digital signature. Digitally signed corporate messages allow identity verificationMany clients, such as Outlook, display an indicator and provide details of the certificate. If a contact you frequently interact with signs their emails, validate that clue.
Content, links and attachments: how to review without falling
If you receive an unexpected but plausible email, investigate outside of the email. Search the company on Google and contact them through their official channels.. Do not use phone numbers or addresses provided in the email itself until you confirm their legitimacy.
With links, apply the golden rule: see first, click later or neverCheck the real URL, run analytics on reputable services, and avoid logging into anything sensitive if you have any concerns. It's best to open a new tab and manually enter the service address.
Regarding attachments, remember the risk formats. Avoid opening .exe, .js, .jar, .bat, .cmd, .vbs, .msi, .hta, .scr, .pif, .reg, .cpl, .wsf, even if the antivirus doesn't flag them. And be suspicious of double extensions like imagen.gif.exe, where the latter takes precedence.
Macros in Office documents. It is a classic technique that has made a strong comebackIf a Word or Excel application asks you to enable content to view the alleged invoice or report, cancel it and check with a trusted source first.
Even seemingly harmless attachments like PDFs or images can be dangerous. Scan it with your antivirus and if you don't expect anything, don't open it.When in doubt, request a resend via an alternative channel or ask for specific details that are difficult to falsify.
Common tactics: from urgency to spoofing
Urgency and fear. They make you react on autopilotThey can simulate account freezes, strange charges, or tax refunds. Impersonation of the Tax Agency is common in Spain, an example of the rise in cyber scams.
Phishing at work. They can pretend to be managers Requesting payments from supposed clients or access confirmations. Verify via chat or internal phone before moving a euro.
Link shorteners. They hide the real destinationIf they arrive by email, scan them first with an external tool and don't browse critical services while logged in.
Email bombing. Clogging your inbox so you miss the important stuff or to filter mass campaigns that subscribe you to newsletters. Filter, sort, and stay on top of key communications during a flood.
Spoofing (sender impersonation). The attacker disguises the From field to appear legitimateIt may appear to be coming from your own domain or from a provider's. If the message appears to be internal but is arriving as external, be suspicious and verify it through another channel.
False legitimizers. Security-looking domains, copied brands, and high-priority labels They seek to deceive by appearances. They aren't proof of anything: the actual domain of the link, its consistency, and your external verification weigh more.
What happens if an email has malware?
If you run the load, They can steal your personal data, credentials or encrypt your filesKeyloggers record keystrokes; spyware profiles your activity; ransomware locks your information and demands a ransom; and a Trojan can open a backdoor to become part of a botnet.
Entry can occur by downloading an attachment, clicking a link that triggers a download, or granting permissions on a document. A single click can be enough to compromise your entire computer. and, in corporate environments, expand through the local network.
How they get your address and how to reduce exposure
Attackers feed their lists from multiple sources. Trackers collect emails posted on websites or forums, chain emails multiply the visibility of addresses and massive leaks end up being sold and circulated for years.
Unencrypted forms, public Wi-Fi networks, and vulnerable sites can expose your email and other data. Avoid entering addresses on unencrypted pages and limit your registrations to trusted services.Consider using disposable emails or aliases for suspicious registrations.
The malware also steals address books. An infected contact can send you malware without knowing it.; treat any unexpected attachment as suspicious, even if it comes from someone you know.
Good practices in the company
Separate accounts. At least one exclusive account for work, another for personal use, and a third for low-value records.This way, you compartmentalize the risk and reduce the impact of leaks and spam.
Protect access. Long, unique passwords, changed periodically, and with multi-factor authentication reduce the likelihood of intrusion, even if they leak your password. Avoid shared accounts with passwords known by multiple people.
Basic privacy. Use blind carbon copy when sending to multiple recipients to avoid exposing addresses and be careful where you post your email. Less distribution, less spam, and fewer targets for targeted attacks.
Continuous training. Phishing simulations, awareness, and clear reporting processes (e.g., forwarding to a secure mailbox or a button in Outlook) increase early detection and prevent impulsive clicks.
Practical advice when you suspect
1) Don't download anything. If you're not expecting an attachment, don't open it.2) Don't reply or interact. 3) Analyze links with reputable tools. 4) Search the internet for references to the sender or the text of the message.
If the email claims to be from a company or bank, contact us through official channels. Do not call the email address itself or reply to the same email address without first checking.
What to do if you've already opened or downloaded something
Delete the downloaded files from that email if you haven't run them yet. This way you avoid activating the charge if you haven't opened it yet.. It doesn't always fix the problem, but it reduces risk.
Update system and applications. Patch vulnerabilities to prevent persistence or escalationCheck Windows Update and updates to your office suite and browser. Disconnect external devices. Separate pendrives or disks to avoid spreadIf you work on a network, consult with IT about temporarily disconnecting the suspect equipment.
Prevent tracking in Gmail and Outlook
Many campaigns use tracking pixels embedded in images. Set your email to not load external images automaticallyIn Gmail, under Settings > See all settings > General > Images, select Ask before showing. In Outlook, under Settings > General > Privacy & Data, turn off service charges.
Useful extensions. Ugly Email and PixelBlock help block tracking in supported browsers. Use them as a backup, not as a replacement for your email client's settings.
Is your account secure? Basic controls
Check your password strength and enable 2FA. Without a strong password and a second factor, you are an easy target.Avoid reuse: a theft in one service drags down the rest.
Use official apps. Install software from trusted sources and avoid dubious third-party clients. Review login history and close suspicious sessions.
Avoid posting your address. The less public exposure your email has, the less spam. and you will receive fewer targeted phishing attempts.
Tools and services that help
Microsoft Defender for Office 365 (Threat Scanner and Real-time Detections). If your organization has Plan 2 (Explorer) or Plan 1 (Real-time Detections), you can investigate and respond in near real-time: search for and delete messages, identify malicious sender IPs, and initiate incidents.
How to search for suspicious delivered mail: 1) Open Explorer or Real-Time Detections2) Select the appropriate view (All Mail, Malware, Phish) and date range (by default, yesterday and today). 3) Create filters based on useful properties: delivery action (delivered, spam, blocked), original and last location, directionality (inbound, intra-org, outbound) to detect spoofing, policy overrides (organization or user), and URL threats (malware, phishing, spam). 4) Update and review the Email tab with key columns to understand the message's path. 5) Export if necessary (up to 200.000 results) and apply corrections by deleting the email from the affected mailboxes.
Simulators and awareness. Platforms like Keepnet Labs allow you to simulate phishing, measure vulnerability and educate, as well as testing your antispam/antivirus and making reporting easier with Outlook add-ins.
Privacy and encryption with Mailfence. Email service focused on end-to-end encryption (AES-256/OpenPGP), digital signatures, and 2FA. Useful for sensitive communications, with enough free options for many users.
Alias ​​with Firefox Relay. Create screen addresses that forward to your real mailboxYou can delete them whenever you want and limit your exposure. Ideal for registrations on services that don't inspire complete confidence.
Verify addresses with Captain Verify. Online tool that validates emails, syntax, and server existence. Useful for debugging lists and detecting fake or expired accounts. Remember: verifying validity does not indicate that an email is secure, only that the address exists.
Block IP in Gmail with extensions. With Block Sender you can block an email source by IP: Identify the IP in the Show Original (Received) header, create a new block on the extension, and decide on its destination (trash, spam). Keep an inventory to revert if necessary.
Why you shouldn't save sensitive information in your email
If your mailbox is attacked, everything stored is exposed: personal data, documents, even passwords you've saved in messages. Third-party apps with access to your account can also read them.
Provider privacy varies and there are flaws. A vulnerability or bad policy can leak your data.. It's better to use password managers and encrypted storage for critical items.
Emails impersonating nearby brands
In Spain, logistics and courier companies are frequent targets. Criminals use the brand to notify of alleged shipments, rates or updates. and thus steal data or make charges. Always check with the official website and avoid paying or entering credentials from a suspicious email.
Typical phishing cases you will see
Suspended accounts that aren't yours, fake 2FA logins, tax returns with bank details, order confirmations with malicious attachments, and internal payment orders. They all share a pattern: haste, believable appearance and a click that they want to force on you..
Use isolated environments to review risky content
If you need to open something dubious, do it in a dedicated, disposable virtual machine (VirtualBox or others). If it breaks, you just erase it and that's it, without touching your main computer.
Another option is to unpack on an old phone without sensitive accounts. Connect it only to WiFi, without critical apps, and use it as a risk zone. Still, don't enter passwords on pages you haven't verified: credential capture doesn't require infecting your device.
Organize your emails by sensitivity
To protect well, Maintain a clean account for key banks, agencies, and businesses, without newsletters or mass registrations. Use another one for forums and testing. This reduces noise and the likelihood of a phishing attack getting through where credentials matter.
If you ever doubt, Remember the golden rule: when you don't see it clearly, don't click or download anything.. Check through another channel, ask IT if you're in the company, and report it so others don't fall for it.
With a mix of common sense, sender and link verification, prudent attachment management, two-factor authentication, disabling external images, using aliases, and tools like Defender for Office 365, Mailfence, or Firefox Relay, You can drastically reduce email risk and stop most malware and phishing campaigns.If you miss one, act quickly: disconnect, analyze, update, and ask for help.
