VBSpam Email Security Comparative Review - September 2021

Ionuţ Răileanu & Adrian Luca

Virus Bulletin

Copyright © 2021 Virus Bulletin

In this test – which forms part of Virus Bulletin’s continuously running security product test suite – eight full email security solutions, one custom configured solution¹, one open-source solution and one blocklist were assembled on the test bench to measure their performance against various streams of wanted, unwanted and malicious emails.

The results show that the tested security solutions performed well. With fewer malware and phishing emails seen in the wild during the period in which this test ran, the challenges came from non-English phishing campaigns and short duration malware campaigns.

For some additional background to this report, the table and map below show the geographical distribution (based on sender IP address) of the spam emails seen in the test. (Note: these statistics are relevant only to the spam samples we received during the test period.)

Malware and phishing

During the period in which this test ran, we saw a decrease in the number of malware and phishing emails compared to previous tests. In the following sections we highlight a few cases that proved to be challenging for the tested solutions to block.

Dridex²

Attachment SHA256:

3e5c3ca2dba4a97b5ce64954a2b4a01b29a140dacfc0401dcc75471545c1f49a
7c927ba1fcda33da30b47aed10a4d3b1ab4dcf5c157acc5ca6e90985a70b1eb1
22c9e35ef6579611c7d2e6db7e3d1c7c7cd203d84919c8f46eeb343583342be5

Name:

taxve_50694104_20210816_63660_25466460.xlsm
taxve_158762_20210816_581617912_0748186.xlsm
taxve_84492685_20210816_053880_415784.xlsm

This was a spam campaign we saw active for only one day: 16 August. The campaign caught our attention because, for the first four hours after the initial occurrence, it managed to bypass the filters of the majority of the tested solutions.

 Email from spam campaign with Dridex attachment.

Zeppelin ransomware³

Attachment SHA256:

84825c5810241c7a092119d19b92165b11774135d9557d7c54212bd6ccaa5a24

Name:

3346.zip

With little text and using a free email service, this malicious email was not part of a campaign – it occurred only once and was missed by half of the tested solutions. The archive contains a .js file that leads to a ransomware associated with the Buran family, more precisely, Zeppelin ransomware⁴.

Email with attached archive containing a .js file that leads to Zeppelin ransomware.

Non-English phishing

As mentioned in the last test report, we continue to see non‑English phishing emails bypassing the filters of most of the tested solutions. Below are screenshots of three phishing campaigns that were active during the 16-day period in which this test ran.

Danish phishing email.

French phishing email.
Romanian phishing email.

Results

The majority of tested solutions managed to block more than 99% of the spam samples. We highlight the performance of the new entry, N-able Mail Assure, which managed to block all the malware and phishing emails. Both Cleanmail and Libraesva also achieved a 100% malware catch rate.

Of the participating full solutions, five achieved a VBSpam award – Axway, Cleanmail, Libraesva, Net at Work and Zerospam – while a further three achieved a VBSpam+ award – Bitdefender, Fortinet and N-able Mail Assure – as did the custom configured solution, Spamhaus DQS.

Axway MailGate 5.6

SC rate: 99.90%
FP rate: 0.17%
Final score: 99.05
Malware catch rate: 98.24%
Phishing catch rate: 99.01%
Project Honey Pot SC rate: 99.87%
Abusix SC rate: 99.91%
Newsletters FP rate: 0.0%
Speed:

10%

50%

95%

98%

Bitdefender Security for Mail Servers 3.1.7

SC rate: 99.94%
FP rate: 0.00%
Final score: 99.94
Malware catch rate: 98.36%
Phishing catch rate: 99.43%
Project Honey Pot SC rate: 99.99%
Abusix SC rate: 99.93%
Newsletters FP rate: 0.0%
Speed:

10%

50%

95%

98%

Cleanmail Domain Gateway

SC rate: 99.99%
FP rate: 0.03%
Final score: 99.64
Malware catch rate: 100.00%
Phishing catch rate: 100.00%
Project Honey Pot SC rate: 99.98%
Abusix SC rate: 99.99%
Newsletters FP rate: 4.9%
Speed:

10%

50%

95%

98%

Fortinet FortiMail

SC rate: 99.80%
FP rate: 0.00%
Final score: 99.80
Malware catch rate: 96.95%
Phishing catch rate: 98.30%
Project Honey Pot SC rate: 99.66%
Abusix SC rate: 99.84%
Newsletters FP rate: 0.0%
Speed:

10%

50%

95%

98%

Libraesva ESG v.4.7

SC rate: 99.88%
FP rate: 0.03%
Final score: 99.68
Malware catch rate: 100.00%
Phishing catch rate: 99.72%
Project Honey Pot SC rate: 99.75%
Abusix SC rate: 99.92%
Newsletters FP rate: 1.0%
Speed:

10%

50%

95%

98%

N-able Mail Assure

SC rate: 99.87%
FP rate: 0.00%
Final score: 99.84
Malware catch rate: 100.00%
Phishing catch rate: 99.50%
Project Honey Pot SC rate: 99.77%
Abusix SC rate: 99.90%
Newsletters FP rate: 1.0%
Speed:

10%

50%

95%

98%

NoSpamProxy

SC rate: 99.84%
FP rate: 0.00%
Final score: 99.74
Malware catch rate: 98.36%
Phishing catch rate: 99.22%
Project Honey Pot SC rate: 99.83%
Abusix SC rate: 99.84%
Newsletters FP rate: 2.9%
Speed:

10%

50%

95%

98%

Rspamd

SC rate: 97.08%
FP rate: 0.93%
Final score: 92.38
Malware catch rate: 87.69%
Phishing catch rate: 80.75%
Project Honey Pot SC rate: 94.33%
Abusix SC rate: 97.90%
Newsletters FP rate: 2.9%
Speed:

10%

50%

95%

98%

Spamhaus Data Query Service

SC rate: 99.63%
FP rate: 0.00%
Final score: 99.60
Malware catch rate: 94.02%
Phishing catch rate: 97.59%
Project Honey Pot SC rate: 99.39%
Abusix SC rate: 99.70%
Newsletters FP rate: 1.0%
Speed:

10%

50%

95%

98%

ZEROSPAM

SC rate: 99.29%
FP rate: 0.14%
Final score: 98.57
Malware catch rate: 92.97%
Phishing catch rate: 96.39%
Project Honey Pot SC rate: 99.35%
Abusix SC rate: 99.27%
Newsletters FP rate: 1.0%
Speed:

10%

50%

95%

98%

Abusix Mail Intelligence

SC rate: 98.77%
FP rate: 0.00%
Final score: 98.64
Malware catch rate: 95.78%
Phishing catch rate: 97.52%
Project Honey Pot SC rate: 98.03%
Abusix SC rate: 98.99%
Newsletters FP rate: 3.9%

Results tables

	True negatives	False positives	FP rate	False negatives	True negatives	SC rate	Final score	VBSpam
Axway	2909	5	0.17%	140.2	143943	99.90%	99.05
Bitdefender	2914	0	0.00%	84.8	143998.4	99.94%	99.94
Cleanmail Domain Gateway	2913	1	0.03%	20.6	144062.6	99.99%	99.64
FortiMail	2914	0	0.00%	294.2	143789	99.80%	99.80
Libraesva	2913	1	0.03%	171	143912.2	99.88%	99.68
N-able Mail Assure	2914	0	0.00%	185	143898.2	99.87%	99.84
NoSpamProxy	2914	0	0.00%	227.4	143855.8	99.84%	99.74
Rspamd	2887	27	0.93%	4201.6	139881.6	97.08%	92.38
Spamhaus DQS	2914	0	0.00%	530.4	143552.8	99.63%	99.60
ZEROSPAM	2910	4	0.14%	1027	143048.2	99.29%	98.57
Abusix Mail Intelligence*	2914	0	0.00%	1770	142313.2	98.77%	98.64	N/A

*This product is a partial solution and its performance should not be compared with that of other products.
(Please refer to the text for full product names and details.)

*This product is a partial solution and its performance should not be compared with that of other products. None of the queries to the IP blocklist included any information on the attachments; hence its performance on the malware corpus is added purely for information.
† The standard deviation of a product is calculated using the set of its hourly spam catch rates.
(Please refer to the text for full product names and details.)

	Speed
	10%	50%	95%	98%
Axway
Bitdefender
Cleanmail Domain Gateway
FortiMail
Libraesva
N-able Mail Assure
NoSpamProxy
Rspamd
Spamhaus DQS
ZEROSPAM

0-30 seconds

30 seconds to two minutes

two minutes to 10 minutes

more than 10 minutes

(Please refer to the text for full product names and details.)

(Please refer to the text for full product names.)

(Please refer to the text for full product names and details.)

(Please refer to the text for full product names and details.)

(Please refer to the text for full product names and details.)

Appendix: set-up, methodology and email corpora

The full VBSpam test methodology can be found at https://www.virusbulletin.com/testing/vbspam/vbspam-methodology/vbspam-methodology-ver20.

The test ran for 16 days, from 12am on 7 August to 12am on 23 August 2021 (GMT).

The test corpus consisted of 147,208 emails. 144,192 of these were spam, 33,091 of which were provided by Project Honey Pot, with the remaining 111,101 spam emails provided by Abusix. There were 2,914 legitimate emails (‘ham’) and 102 newsletters, a category that includes various kinds of commercial and non-commercial opt-in mailings.

136 emails in the spam corpus were considered ‘unwanted’ (see the June 2018 report⁵) and were included with a weight of 0.2; this explains the non-integer numbers in some of the tables.

Moreover, 853 emails from the spam corpus were found to contain a malicious attachment while 1,413 contained a link to a phishing or malware site; though we report separate performance metrics on these corpora, it should be noted that these emails were also counted as part of the spam corpus.

Emails were sent to the products in real time and in parallel. Though products received the email from a fixed IP address, all products had been set up to read the original sender’s IP address as well as the EHLO/HELO domain sent during the SMTP transaction, either from the email headers or through an optional XCLIENT SMTP command⁶.

For those products running in our lab, we all ran them as virtual machines on a VMware ESXi cluster. As different products have different hardware requirements – not to mention those running on their own hardware, or those running in the cloud – there is little point comparing the memory, processing power or hardware the products were provided with; we followed the developers’ requirements and note that the amount of email we receive is representative of that received by a small organization.

Although we stress that different customers have different needs and priorities, and thus different preferences when it comes to the ideal ratio of false positive to false negatives, we created a one-dimensional ‘final score’ to compare products. This is defined as the spam catch (SC) rate minus five times the weighted false positive (WFP) rate. The WFP rate is defined as the false positive rate of the ham and newsletter corpora taken together, with emails from the latter corpus having a weight of 0.2:

WFP rate = (#false positives + 0.2 * min(#newsletter false positives , 0.2 * #newsletters)) / (#ham + 0.2 * #newsletters)

while in the spam catch rate (SC), emails considered ‘unwanted’ (see above) are included with a weight of 0.2.

The final score is then defined as:

Final score = SC - (5 x WFP)

In addition, for each product, we measure how long it takes to deliver emails from the ham corpus (excluding false positives) and, after ordering these emails by this time, we colour-code the emails at the 10th, 50th, 95th and 98th percentiles:

	(green) = up to 30 seconds
	(yellow) = 30 seconds to two minutes
	(orange) = two to ten minutes
	(red) = more than ten minutes

Products earn VBSpam certification if the value of the final score is at least 98 and the ‘delivery speed colours’ at 10 and 50 per cent are green or yellow and that at 95 per cent is green, yellow or orange.

Meanwhile, products that combine a spam catch rate of 99.5% or higher with a lack of false positives, no more than 2.5% false positives among the newsletters and ‘delivery speed colours’ of green at 10 and 50 per cent and green or yellow at 95 and 98 per cent earn a VBSpam+ award.

Footnotes

¹ Spamhaus DQS is a custom solution built on top of the SpamAssassin open-source anti-spam platform.

² https://bazaar.abuse.ch/sample/3e5c3ca2dba4a97b5ce64954a2b4a01b29a140dacfc0401dcc75471545c1f49a https://twitter.com/reecdeep/status/1427285423773175813

³ https://tria.ge/210811-al1kb163g2/behavioral2

⁴ https://www.pcrisk.com/removal-guides/16540-zeppelin-ransomware

⁵ https://www.virusbulletin.com/virusbulletin/2018/06/vbspam-comparative-review

⁶ http://www.postfix.org/XCLIENT_README.html

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