Avoid having your email account stolen via fake "Signed Invoice" emails
Written by Tomas Meskauskas on
What kind of email is "Signed Invoice"?
After inspecting this "Signed Invoice" email, we determined that it is spam. The message claims that the recipient could not be otherwise contacted, so they have been sent the invoice via email. This is a phishing campaign that targets email account log-in credentials through fake document-sharing websites.
"Signed Invoice" email scam overview
The spam email with the subject "Signed Invoice" (may vary) claims that the sender failed to reach the recipient via phone call. Hence, they were sent the signed invoice through an email, per the instructions of the sender's boss. The letter requests confirmation that the invoice was received.
It must be emphasized that the information in this email is false, and this mail is not associated with any real individuals or legitimate entities.
As mentioned in the introduction, the "Signed Invoice" spam campaign promotes a phishing scam. Interestingly, it endorses phishing sites both through a link in the email and the attachment. The webpage opened via the link in the body of the letter is presented as a blurred Microsoft Excel document. The fake file is overlaid by a pop-up instructing the user to sign in with their email provider to access the shared documents.
The attachment – "Doc 25112024.pdf" (filename may vary) – appears as a blurred document overlaid by an Adobe PDF icon and text claiming that it is a "Secured PDF Online Document", the button below reading "View on Adob e". Interacting with this file produces a redirect to a different phishing website.
Much like the other page, this one also depicts a blurred document. However, this webpage imitates the Adobe website. The pop-up atop the supposed document requests the user to confirm their identity with their active email account.
Phishing sites record provided information and send it to scammers; in this case, the targeted data are email log-in credentials (passwords). Emails are highly sought by scammers since they tend to contain highly sensitive information and might be used to hijack the accounts, platforms, and services registered through them.
To expand upon how stolen accounts can be abused, cyber criminals can steal owners' identities (e.g., emails, social networking, social media, messengers, etc.) and request loans or donations from contacts/friends/followers, promote scams, and proliferate malware by sharing malicious links or files.
Hijacked finance-related accounts (e.g., e-commerce, money transferring, digital wallets, online baking, etc.) can be used to make fraudulent transactions or online purchases.
To summarize, victims of scam mail like "Signed Invoice" can experience severe privacy issues, financial losses, and identity theft.
If you have already disclosed your account credentials – change the passwords of all potentially compromised accounts and contact their official support without delay.
| Name | "Signed Invoice" phishing email |
| Threat Type | Phishing, Scam, Social Engineering, Fraud |
| Fake Claim | Recipient has been sent a signed invoice since they could not be contacted by phone. |
| Attachment(s) | Doc 25112024.pdf (filename may vary) |
| Related Domains | emailtrace.datasetn[.]site |
| Detection Names (emailtrace.datasetn[.]site) | Combo Cleaner (Malware), Fortinet (Phishing), G-Data (Malware), Kaspersky (Phishing), Sophos (Phishing), Full List Of Detections (VirusTotal) |
| Serving IP Address (emailtrace.datasetn[.]site) | 104.21.88.247 |
| Symptoms | Unauthorized online purchases, changed online account passwords, identity theft, illegal access of the computer. |
| Distribution methods | Deceptive emails, rogue online pop-up ads, search engine poisoning techniques, misspelled domains. |
| Damage | Loss of sensitive private information, monetary loss, identity theft. |
| Malware Removal (Windows) | To eliminate possible malware infections, scan your computer with legitimate antivirus software. Our security researchers recommend using Combo Cleaner. |
Phishing spam campaign examples
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In addition to the log-in credentials of various accounts, these messages commonly seek personally identifiable information and finance-related data. However, other scams are promoted through spam mail as well, and it is utilized in malware distribution.
Widely used lures include claims concerning invoices/payments, business offers, account/service issues, expired passwords, security upgrades, refunds, lotteries, inheritances, and so forth.
While spam emails are often poorly written and full of grammatical/spelling mistakes, they can be competently put together and even convincingly disguised as messages from legitimate entities (e.g., companies, organizations, service providers, authorities, etc.).
How do spam campaigns infect computers?
Spam campaigns distribute malware through malicious files that can be attached to or linked inside the emails/messages. These files come in various formats, e.g., documents (PDF, Microsoft Office, Microsoft OneNote, etc.), executables (.exe, .run, etc.), archives (ZIP, RAR, etc.), JavaScript, and so on.
Merely opening an infectious file can be enough to trigger malware download/installation. Some formats need additional user interaction to initiate infection processes. For example, Microsoft Office files require users to enable macro commands (i.e., editing/content), while OneNote documents need them to click on embedded links or files.
How to avoid installation of malware?
We strongly recommend caution with incoming emails, DMs/PMs, SMSes, and other messages. Attachments or links found in dubious/irrelevant mail must not be opened, as they can be harmful or virulent.
It must be mentioned that malware is spread using various methods. Therefore, we advise vigilance when browsing since the Internet is full of well-disguised fake and dangerous content.
Furthermore, all downloads must be performed from official and trustworthy sources. Another recommendation is to activate and update programs using functions/tools provided by genuine developers, as illegal product activation tools ("cracks") and third-party updaters can contain malware.
It is paramount for device/user safety to have a reputable anti-virus installed and kept updated. This software must be used to run regular system scans and to remove detected threats. If you've already opened malicious attachments, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate infiltrated malware.
Text presented in the "Signed Invoice" spam email letter:
Subject: Signed Invoice
Scanned_documents.xls | 1 file (total 387.5 KB) VIEW | DOWNLOAD
Dear Sir/Madam,
I tried to reach you over the phone but unable to reach you.
As directed by my boss, please find attached Signed Invoice for your attention.
Acknowledge receipt of mail.
Best Regards.
Screenshot of the phishing website promoted via link in the spam email:
Screenshot of the file attached to this spam email ("Doc 25112024.pdf"):
Screenshot of the phishing website promoted by this attachment:
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Quick menu:
- What is "Signed Invoice" phishing email?
- Types of malicious emails.
- How to spot a malicious email?
- What to do if you fell for an email scam?
Types of malicious emails:
Phishing Emails
Most commonly, cybercriminals use deceptive emails to trick Internet users into giving away their sensitive private information, for example, login information for various online services, email accounts, or online banking information.
Such attacks are called phishing. In a phishing attack, cybercriminals usually send an email message with some popular service logo (for example, Microsoft, DHL, Amazon, Netflix), create urgency (wrong shipping address, expired password, etc.), and place a link which they hope their potential victims will click on.
After clicking the link presented in such email message, victims are redirected to a fake website that looks identical or extremely similar to the original one. Victims are then asked to enter their password, credit card details, or some other information that gets stolen by cybercriminals.
Emails with Malicious Attachments
Another popular attack vector is email spam with malicious attachments that infect users' computers with malware. Malicious attachments usually carry trojans that are capable of stealing passwords, banking information, and other sensitive information.
In such attacks, cybercriminals' main goal is to trick their potential victims into opening an infected email attachment. To achieve this goal, email messages usually talk about recently received invoices, faxes, or voice messages.
If a potential victim falls for the lure and opens the attachment, their computers get infected, and cybercriminals can collect a lot of sensitive information.
While it's a more complicated method to steal personal information (spam filters and antivirus programs usually detect such attempts), if successful, cybercriminals can get a much wider array of data and can collect information for a long period of time.
Sextortion Emails
This is a type of phishing. In this case, users receive an email claiming that a cybercriminal could access the webcam of the potential victim and has a video recording of one's masturbation.
To get rid of the video, victims are asked to pay a ransom (usually using Bitcoin or another cryptocurrency). Nevertheless, all of these claims are false - users who receive such emails should ignore and delete them.
How to spot a malicious email?
While cyber criminals try to make their lure emails look trustworthy, here are some things that you should look for when trying to spot a phishing email:
- Check the sender's ("from") email address: Hover your mouse over the "from" address and check if it's legitimate. For example, if you received an email from Microsoft, be sure to check if the email address is @microsoft.com and not something suspicious like @m1crosoft.com, @microsfot.com, @account-security-noreply.com, etc.
- Check for generic greetings: If the greeting in the email is "Dear user", "Dear @youremail.com", "Dear valued customer", this should raise suspiciousness. Most commonly, companies call you by your name. Lack of this information could signal a phishing attempt.
- Check the links in the email: Hover your mouse over the link presented in the email, if the link that appears seems suspicious, don't click it. For example, if you received an email from Microsoft and the link in the email shows that it will go to firebasestorage.googleapis.com/v0... you shouldn't trust it. It's best not to click any links in the emails but to visit the company website that sent you the email in the first place.
- Don't blindly trust email attachments: Most commonly, legitimate companies will ask you to log in to their website and to view any documents there; if you received an email with an attachment, it's a good idea to scan it with an antivirus application. Infected email attachments are a common attack vector used by cybercriminals.
To minimise the risk of opening phishing and malicious emails we recommend using Combo Cleaner Antivirus for Windows.
Example of a spam email:
What to do if you fell for an email scam?
- If you clicked on a link in a phishing email and entered your password - be sure to change your password as soon as possible. Usually, cybercriminals collect stolen credentials and then sell them to other groups that use them for malicious purposes. If you change your password in a timely manner, there's a chance that criminals won't have enough time to do any damage.
- If you entered your credit card information - contact your bank as soon as possible and explain the situation. There's a good chance that you will need to cancel your compromised credit card and get a new one.
- If you see any signs of identity theft - you should immediately contact the Federal Trade Commission. This institution will collect information about your situation and create a personal recovery plan.
- If you opened a malicious attachment - your computer is probably infected, you should scan it with a reputable antivirus application. For this purpose, we recommend using Combo Cleaner Antivirus for Windows.
- Help other Internet users - report phishing emails to Anti-Phishing Working Group, FBI’s Internet Crime Complaint Center, National Fraud Information Center and U.S. Department of Justice.
Frequently Asked Questions (FAQ)
Why did I receive this email?
Regardless of any relevant information that spam emails may include, they are not personal. This mail is distributed in massive operations – hence, thousands of users receive identical (or incredibly similar) emails.
I have provided my personal information when tricked by this spam email, what should I do?
If you have provided your log-in credentials – change the passwords of all potentially exposed accounts and inform their official support without delay. However, if you have disclosed other private information (e.g., ID card details, passport photos/scans, credit/debit card numbers, etc.) – immediately contact the appropriate authorities.
I have read a spam email but didn't open the attachment, is my computer infected?
No, opening/reading an email will not trigger any malware download/installation chains. Systems are infected when malicious attachments or links are opened/clicked.
I have downloaded and opened a file attached to a spam email, is my computer infected?
Whether the device was infected depends on the file's purpose (i.e., phishing or malware infiltration). Its format might also be relevant for whether the system was compromised.
Once opened, executables cause infections almost without fail. However, some formats – like documents – may need extra interaction to trigger malware download/installation. In these cases, the infection is only initiated after macro commands are enabled, embedded content is clicked, or other actions are performed.
Will Combo Cleaner remove malware infections present in email attachments?
Yes, Combo Cleaner is capable of detecting and removing practically all known malware infections. It must be stressed that performing a complete system scan is crucial since sophisticated malicious programs tend to hide deep within systems.
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