Misleading concepts about Email Security Gateways are being spread by new players of the email security industry

Cisco’s SpamCop service: worldwide outage after its domain expired

Yesterday most of the mail administrators, organizations, and MSPs worldwide suddenly found that their mail was being rejected as it reported as being listed in the blacklist at bl.spamcop.net.

SpamCop, a wholly-owned subsidiary of Cisco Systems, provides a Real-time Blackhole List (RBL) that mail servers can use to determine if incoming mail should be marked as spam, suffered a worldwide outage after its domain mistakenly was allowed to expire.

As a consequence of this all cloud services and mail servers – including Libraesva, Cisco and Barracuda only to mention a few – who use their RBL started to reject incoming mail automatically.

According to a post on Reddit, when visiting spamcop.net, the domain was shown as parked , and users that tried to contact Cisco didn’t get any answer. Libraesva has contacted Cisco as well with further questions but has not received any reply from them as of yet.

Sunday evening finally Cisco renewed the spamcop.net domain, but some customers and mail administrators are still reporting that they continue to see issues with their incoming mail being blocked by SpamCop. This is due to the DNS systems dealing with cache and TTL. We suggest to manually expire DNS cache before re-enable the SpamCop RBL Service.

We do apologize with all Libraesva’s customers for any inconvenience that we may have caused relying on SpamCop RBL.

Earlier in December another big company offering cloud storage – Wasabi – had a worldwide outage caused by its domain being suspended by GoDaddy and taking down on their knees all customers worldwide, being unable to resolve their object storage bucket.

It seems that simple tasks like keeping a service domain active and healthy are huge problems for these industry giants… Nevertheless if this is a mission critical task with worldwide impact.



Mimecast® for Microsoft 365™ hacked

A few days ago, Microsoft® informed that a Mimecast® for Microsoft 365™ certificate has been hacked and is being used against Mimecast’s customers.

This certificate allows full administrative access to the Microsoft 365Exchange Web Services of some Mimecast’s customers, estimated to be around 10% of their global install base, who had configured the integration between Mimecast® and Microsoft 365.

Since this announcement was made, we have been asked by our channel partners and customers if the integration between Libraesva’s products and Microsoft 365 can be abused in the same way.

The short answer is no. The long answer is no, because…

1) We do not use a single certificate to authenticate against our customer’s Microsoft 365 tenants.

Libraesva products (Email Security Gateway and Email Archiver) authenticate to Microsoft 365 using credentials that are unique for each tenant.

A single certificate that acts as a passe-partout key for full access to many customer’s tenants is a bad design choice from a security standpoint. This is, of course, our opinion.

2) We instruct our customers to provide to Libraesva with the minimum set of permissions we require.

Libraesva asks for the minimum set of permissions required to provide the services we provide. We do not advise our customers to provide complete access to their own tenants. We ask them to only provide the permissions that they need, based on how they use our products.

3) We have a de-centralized architecture.

Libraesva’s products are designed for full isolation between customers. Each customer ‘lives’ in a separate virtual appliance, with a unique IP address. We do not store access credentials in any central repository.

As Libraesva is a security company, we know that security is difficult and that anybody can fail. Our architectural and software design choices are based on strict security principles, among which is avoiding any single point of failure.

What is a secure email gateway and why you need it

The last year, maybe like no year before, demonstrated clearly just how much every moment and aspect of our day-to-day lives depend on the Internet. This dependence leads to an increase of risks and threats to our “online security”.

According to the latest Data Breach Investigation Report, email is still the main vehicle for delivering cyber threats, with particular reference to malicious links and attachments which are developed in order to carry malware. 46% of those surveyed included companies who said they had received the bulk of malware delivery attempts via email. Social Engineering attacks also remain very high, around 96%, and phishing is confirmed the favourite form, while successful Business Email Compromise deliveries has led to an average loss of $ 44,000 per company.

Why email?

According to a Radicati Group’s study, there will be more than 4.2 billion email users within the first months of 2022; this means that about half of the global population will be using email to communicate. Consequently, a cyber attack delivered via email has a high chance of being successful and spreading like wildfire.

For example, let’s think about the Account Takeover phenomenon, a fraudulent identity theft attack method: cybercriminals obtain a victimis’ account credentials through brand impersonation, phishing and social engineering techniques and then monitor an organisations activities to learn how the company does business, manages financial transactions and even communicate with one another. This allows the cybercriminal to glean valuable information to resell to competitors, damage a companies reputation or bottom line, generate and spread further cyber attacks or acquire further credential logins, creating an endless cycle.

A single malicious email can cause a significant amount of damage to networks and, in some cases, completely halt business growth. This is exactly why email protection should be considered a crucial part of any businesses cyber-security strategy. Investing in email security is not an expense, but a saving. While it may seem convenient to use free secure email gateways, there are drawbacks to consider, such as the lack of real-time updates to block emerging threats or a lack of comprehensive security features. During the last year we have witnessed how cybercriminals rapidly change their strategies to become more effecient at delivering succesful attacks, circumventing free and simple to manouvere security platforms, negating cost saving benefits realised by implementing free email protection there resulting in larger costs to fix and recover from them – bringing the total cost of a free solution, to many thousands of pounds more expensive than if they had paid for one which can offer real-time protection and the use of a combination of advanced technologies, including artificial intelligence and machine learning, enabling predictive threat analysis.

What is a secure email gateway?

A secure email gateway is essentially a firewall that scans your incoming email in order to protect your mailbox from email-borne cyber threats, such as phishing attacks, compromised business emails, malware, next-generation spam, or fraudulent content of various kinds. But a secure email gateway can also scan outgoing messages to prevent sensitive data from leaving an organization.

What do you need to consider when choosing a secure email gateway?

Choosing a secure email gateway can be a long and difficult process. There are many gateways available on the market and, even if they look very similar, there are numerous differences. To help you along this path, we have suggested some points that you should take in consideration:

  • Deployment: it is important to have the possibility to choose between a cloud and local service, based on the needs of your organization
  • Threat intelligence, artificial intelligence and machine learning technologies, to detect and block both emerging & known threats and help administrators to understand which attack techniques and strategies are used the most against their company
  • Active analysis of URLs and attachments, to quickly and accurately block various types of malware spread in this way, thus preventing phishing attacks
  • Response capabilities, to recognise a malicious email and automatically identify and block all subsequent ones
  • Control of outgoing content to prevent sensitive data from being released

What are the advantages of using a secure email gateway?

First and foremost, a secure email gateway helps to plug gaps in email security. It is a big mistake to think that installing an antivirus engine will protect you against threats delivered via email, or to believe that solutions such as Microsoft365™ (formerly Office365™), offer a complete and secure email gateway service. A recent test carried out on numerous implementations of Microsoft365™ lasting for 1321 days across 175.110 users and 109.284.844 emails, demonstrated that a large number of threats were not intercepted by security filters included in the solution. Unfortunately, cybercriminals have become very good at finding strategies to circumvent software such as antivirus and multi-vector attacks, which use evasion techniques, such as anti-forensics and encryption, expanding significantly in recent years; exactly why nearly 35% of organizations that have switched to Microsoft365™ are integrating their native email security features with a third-party product that combines threat intelligence with traditional filters.

Furthermore, these malicious actos are well aware that employees are the weak link in the chain and the main vehicle for intrusion into corporate networks: the presence of a secure email gateway allows companies to improve employee safety by blocking unsafe URLs and malicious attachments, which are capable of spreading phishing attacks, compromised business emails, malware, and more.

Another advantage of using a secure email gateway is the ability to preserve the operational continuity of email; in the unlikely instance of a primary server experiencing downtime, a secure email gateway can allow users to send and receive email messages through their web interface.

Another feature that a secure email gateway should offer is quarantine management, to allow users to examine blocked messages and log search in a flexible and customizable way, providing comprehensive reports and useful information to help them decide which messages to release, which senders to blacklist and much more.

Finally, the right email gateway offers maximum security, requires minimal maintenance and operates largely in the background in a “set and forget” manner, guaranteeing continuous protection with minimal use of human and time resource.

Why it’s important to test your email security

The significance of email communication in the modern business world cannot be overstated – hundreds of email messages are sent and received daily by even the smallest companies, containing confidential and personal information such as clients’ data, competitive advantages, financial data or just private information.

The global shift to remotely working culture due to the COVID-19 pandemic has empowered cybercriminals to launch highly sophisticated cyberattacks. Moreover, ransomware, phishing, BEC attacks, etc. are amongst the most common types of data breaches that we have witnessed this year, till now.

Over the years, attackers have looked for new ways to gain access to an organization’s network. Years ago, it was SQL Injection attacks. More recently the industry has been plagued with remote desktop-based attacks. But throughout the years, one attack vector has remained near or at the top of the list: email.

According to a study done by Radicati Group in 2020, there will be more than 4.2 billion email users by the start of 2022. Bringing it closer, it means that about half the entire planet uses email right now!

So it’s no surprise that email is still the number one attack vector also in 2020. That’s why it’s important to test your email security. And you will be impressed by how many different ways there are to steal personal information or install malware with an email message: attachments, links, scripts, tracking bugs, macro enabled Office documents, macro-less ones, PDFs or viruses, just to mention a few.

Many IT security professionals assume their email security is performing reasonably enough, until a user reports that he has received a phishing email or when their Security Incident and Event Management (SIEM) solution alerts that your network has been breached.

If you are among the lucky minority that hasn’t seen an attack recently, don’t assume that your email security is just fine because an attack has not been discovered, or just because you have an email security solution in place: test it!

We at Libraesva, developed a free, exclusive Email Security Tester (https://emailsecuritytester.com) that you can use as email self assessment tool, so you can discover where the holes and gaps are in your defenses. Once you know where they are you can do something about it. Don’t wait for someone else to discover it!

We are dedicated only to email security problems, and we are constantly updating our test with the latest tricks that we see in the wild, so you can effectively test your email security. The Test is non-intrusive and private, no client integration or installation is required. It’s completely safe and will not disrupt operations. Minimal details are required to begin the test, so low impact on resources. The test is free and there’s no obligation to buy anything.

Do test your email security now!

The mysterious protocols: SPF, DKIM and DMARC explained

Email is an ancient thing, it was born much longer before the Internet.

The first email system was born in 1965 at MIT. At that time email communication was limited within the boundaries of a single mainframe, those huge and very expensive and delicate multi-user computers that occupied entire air-conditioned rooms and required continuous supervision.

In 1971, the first transmission of an email between connected computers happened. It was a small step for a single email, but a first huge step for humankind.

In 1982, the SMTP protocol was born, this is the protocol we still use today to exchange email on the internet.

The main issue about email (and SMTP) is that, being born in a collaborative environment where security wasn’t an issue at all, being designed at a time where abuse was not even an theoretical option, the protocol did not have any security at all among it’s design requisites.
No authentication of the sender: anybody could pretend to be anyone.
No confidentiality: messages were exchanged and stored in clear.
No integrity checks: manipulations of the email content along the path could not be prevented or even detected.
No protection about unsolicited messages: anybody could send any amount of email to any recipient.

Then email became popular and these issues started quickly to pop up.

It became clear that we needed to do something in order to address this lack of security in the protocol. Nobody had thought about it earlier because nobody envisioned that email would become what it is today: the main form of electronic communication that our societies are based on, something that all organizations, businesses and individuals rely on every day in order to run their lives.

As we all learned the hard way in the following years, adding security afterwards is much more difficult than putting it in at design time. This is one of the most important principles of GDPR: if you want real security you need it by design.

Adding security as an afterthought is hard. It is even harder if you have to guarantee backward-compatibility. Email is the most clear example of how hard is to add security to something that is already deployed worldwide—where you have to guarantee that email can still be exchanged with servers that are not upgraded to the new standards.

This is where the acronyms that are in the title of this article come into play: SPF, DKIM and DMARC are three standards that have been added to the email in the attempt to make it more secure.

SPF has a very simple task: prevent domain spoofing. Your organization can declare to the world a subset of IP addresses authorized to send email on behalf of your organization’s domain. By defining this policy, you can prevent malicious actors sending email pretending to be your organization.
The configuration of an SPF policy is very easy and relatively risk-free: you just need to map all the IP addresses that your organization uses to send email. A little effort for what you receive in exchange, and if you correctly enumerated all your legitimate IP addresses you send email from, no email will get lost.
SPF isn’t perfect, though, and it is not sufficient to prevent all types of spoofing, but it is still much better than nothing.

DKIM has a main purpose: guarantee the integrity of the email content. Integrity means that the recipient can detect if the email has been modified or tampered with along the path. This is done through an electronic signature: if the signature is valid, you know that you can rely on the content of the email. If the signature is invalid, then the message has probably been tampered with. This signature is automatically added and checked by mail servers, and the user doesn’t need to do anything.
Setting up DKIM requires a little more effort than SPF but it is safe: if you misconfigure it, email will not get lost.

SPF and DKIM still don’t completely solve the phishing problem. Email is a little bit like a plain paper letter: the sender and the recipient written on the envelope are used for the delivery, but the recipient does not see the envelope. The recipient just sees the letter inside the envelope, and in that letter the name and address of the sender can be spoofed. Basically, the email client shows the sender that is written in the letter, not the one on the envelope (which can be protected with SPF).

DMARC has been designed exactly for this purpose: making sure that the sender that your email client shows is reliable. This is done by publishing a DMARC policy that instructs the recipients to check if the sender displayed to the recipient matches either with SPF or DKIM. The email must be sent from an authorized IP address for that domain (SPF is ok), or it must be signed with a legitimate key of that domain (the DKIM signature is ok), otherwise it will not be delivered.

DMARC must be configured on a domain by domain basis by the email administrator of the sending domain. It provides great protection against spoofing and impersonation, but the configuration is not straight-forward and mistakes in the configuration can lead to email loss. Therefore, configuring DMARC must be done with expertise, without improvising.

There are other standards that have been introduced in email, like TLS (to encrypt the email in transit) and S/MIME or PGP for end-to-end encryption. These are things you don’t need to care about. TLS is automatically managed by mail servers. S/MIME and PGP have minuscule adoption because of the complexities related to the key management by the end users.

Should you care about SPF, DKIM an DMARC for your organization? Yes, you should.
Start with SPF, then proceed with DKIM and finally evaluate DMARC.

These configurations will not solve all email security problems, but they will make your email communication much more secure and reliable.
Keep in mind that under the hood email is much more complex than it looks on the surface, so consult with an email expert in order to be effective and avoid trouble.

Libraesva ESG v4.8 Release Notes

New wave of EXCEL 4.0 malware campaigns abusing FORMULA macro function

VBA has been introduced in Excel 5.0. Before then Excel only had XLM macros, which are still supported today.

XLM macros allow writing code by entering statements directly into cells, just like normal formulas. In fact they are called macro-formulas.

In case you are curious, the reference document of the Excel 4.0 macro functions is here.

There are a few statements among these macro-formulas that allow executing malicious code, these are named EXEC, RUN and CALL. Last month, in April 2020, a wave of malware abusing these calls has circulated.

In May we’ve seen a new wave that apparently still abused XLM macros but without calling EXEC, RUN or CALL. At the time we got them, most of these samples had a 0 detection rate on virustotal, so they seemed to be worth investigating.

Some of these files were using additional tricks to confuse the analysis, like putting the macros in “hidden” sheets. Some others used “very hidden” sheets, some were protected with the “VelvetSweatshop” password (which is a trick used by Microsoft to define read-only documents). There is also a great variability in file names and email campaigns. I won’t waste time on these details and will get straight to the point.

Here is what you see when opening one of these samples:

macro promt

This is the macro prompt shown by Excel when opening the document

This is the usual Macro prompt from Excel. Nothing unusual.

Then this is how the document appears after either accepting or declining the “enable macro” prompt.

The malicious document as soon as it is opened

Again, nothing unusual here. This is just one of the samples, there are of course many variants but, again, we don’t care.

In this case the sample has two visible sheets. As I said before some of the sample have invisible sheets but this is also not important for our analysis.

What all these samples have in common is the abuse of the FORMULA macro-formula. The recursive naming may create some confusion so let me provide a bit of clarification: just like any other formula statement (like IF or SUM for example), the statement FORMULA can be entered into a cell in the form of a formula. This particular statement happens to be named FORMULA itself.

What does this FORMULA statement do? It enters a formula in the active cell (or in a reference). Basically what is given as a parameter to this call becomes a fomula.

Indirect formula generation if you wish and, yes, it is dangerous as it sounds.

While it is quite clear that the following formula may be dangerous

=EXEC("C:\tools\nc.exe 443 -e cmd.exe") 

it may not be immediately clear that the following one is


An this is basically how these malicious samples behave: they crate a formula by gathering data from lots of different cells and making some transformations. Then they apply the formula by using the FORMULA.FILL statement (or one of it’s variants, see the functions reference linked above if you are interested).

The exact text of the FORMULA is built at runtime and this ensures obfuscation which seems to be effective given the zero or very low scores that these samples got on Virustotal.

This is a glance of what you see by analyzing one of these samples with Decalage‘s olevba:

Tiny portion of the olevba output for one of these samples

I’ve highlighted the FORMULA.FILL function call. There are tens of these calls in any given sample.

We are not interested in reverse-engineering each sample in order to find out the details of the behavior. As an email security company we focus on the methods and the tools used by the attackers rather than on the specific malware variant.

Our job is to block these threats on the gateway, we know that the approach of recognizing known malicious stuff is not effective and therefore we focus on removing the tools that the attackers use.

The philosophy of our QuickSand sandbox is more similar to a firewall: when our systems see a pattern like these they don’t really care about reverse-engineering the actual behavior, they don’t even care about recognizing whether this is a known malware variant or a new one.

Whether it is direct or indirect, any way of executing stuff is not allowed for documents delivered via email. This approach is less prone to evasion and it is proactive: it blocks current and future, known and unknown variants.

The low detection rate of these samples on virustotal and on many sandboxing services based on virtualization confirms that in order to be effective with ever-changing threats this is a better approach.


Rodolfo Saccani / Security R&D Manager @ Libraesva