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消失的網絡釣魚 – 基礎知識


We all know what phishing is and how prevalent it is. This is the attack that accounted for more than 80% in 2021! More details can be found here and here.

With such scary numbers, it is an attack vector that warrants our attention. As we know, the security at our company is only as strong as our weakest link, and unfortunately, this is how threat actors leverage phishing attacks against us.

You can have all controls in the world, but you can still get phished; it is virtually impossible to implement an anti-phishing solution that will cover all the bases. Yes, you can have safe links, and a myriad of other controls, but that user interaction that’s at the core of this attack is how you get exploited and it’s just too difficult to account for. There are many tools out there that will do filtering for you (and whatever else), however these emails still can (and probably will) get through. You need to know what to do when that (inevitably) happens.

This all goes to say how important our education and cyber awareness in the organization are since we can be sure that we will eventually get targeted by one of these attacks.

My goal in this series is to look at and explain how a phishing attack works and how to analyse a phishing email. I will only explain some of the most important things briefly in this article. In the upcoming article, I will dive into the technical aspects of the attack.


Some Historical Context

Phishing and Spam are extremely common social engineering attacks, and not that new at all. First spam message dates all the way back to 1978 – you can read more about that here.

In the 4+ decades this attack has existed, threat actors have found creative ways to perfect it, and we’re all witnessing the results of that effort. As mentioned above, phishing is how 80% of breaches had started in 2021. We can’t know with certainty, but don’t expect this attack to fall out of favor. It is just too convenient for the attacker to at least try and phish the unsuspecting employee.

After obtaining those credentials, they’re off to the races.

Types of Phishing Attacks

Below are listed some of the phishing attack variants:

  • Phishing – Emails sent to the target, appearing to be from a legitimate source with the goal to obtain sensitive information
  • Vishing – Attack that’s based on calling the target on their mobile phone. Same logic and goal as for the regular phishing email
  • Smishing – Same as vishing, with the difference being the attacker is now sending specifically crafted SMS messages to their targets
  • Spear phishing – As phishing, but targeted at a specific individual or organization
  • Whaling – As spear phishing but targeted at C-level executives. Also known as CEO Fraud
  • Spam – Sending of unsolicited emails in bulk to a large group of people

The MO here is almost the same for every variant, even though they might leverage different methods.


Typical Phishing Email

A typical phishing email will have some (or all) of these characteristics:

  • Urgency – Almost invariably, the email will be urgent in one way or the other; be it your ‘reward’ that you just got (you claiming it would be on a timer/urgent), or be it something you need to pay to avoid penalty. It will call you to action, hoping you would react immediately
  • Bad grammar/spelling – This one is quite common and is oftentimes a really good indicator. Most of the phishing attacks will have small grammar/spelling errors within the email. Read through everything carefully. Of course, if an email is written perfectly, it can still be a phishing email
  • Mismatched domains – Email is claiming to be from one company (domain) but it is actually sent from or another domain. Misspelling is also sometimes use to hide the illegitimate domain by tricking you into thinking the domain’s good. Example:,,, etc. also known as Typosquatting – more on that here
  • Suscpicious links/attachements – Unsolicited attachements are sent to you in an email, probably also prompting you to act on them.
  • The sender email address will act and try to appear as a trusted entity – email spoofing
  • The body of the email uses generic addressing such as Dear Sir/Madam, etc.
  • Hyperlinks – oftentimes shortened with URL shortening services so it can hide its true purpose; don’t click on these! Hover over them to see the destination
  • The body of the email is crafted in such a way that it matches a trusted entity (Google, Microsoft, for example)

This is very important to note. There are some good examples out there that illustrate the above nicely, while giving you a practical on the topic. Most companies will use similar stuff when training their employees (most likely with an internal mock phishing test). To see how you fare, you can try the quiz here.

Of course, even if we’re mindful of the above, human error can occur, so you should always pay extra attention when an unknown email pops in your inbox.

How does an Email Travel

Upon hitting SEND in your favorite email client app, there’s a lot of stuff that happens behind the curtains for your email to arrive at its destination. Three protocols are involved in this: POP3, IMAP, and SMTP.

POP3 – Post Office Protocol – receiving emails, downloading from the server

SMTP – Simple Mail Transfer Protocol – handles the sending of the emails

IMTP – Internet Message Access Protocol – stores messages on the server and syncs them across multiple devices

Slightly longer explanation can be found in this article:


Emails are stored on the server (meaning they can also be downloaded on multiple devices)

Sent emails are stored on the server

Messages can be synced and accessed from multiple devices


Emails are downloaded (and stored) on a single device

Sent emails are stored on a single device, from which the email was sent

To keep messages on the server you need to enable “Keep email on server” option, because all the emails would be deleted from the server, once downloaded to the single device

Emails can only be accessed from a single device (where they were downloaded to)


By using SMTP, you’re sending, relaying, or forwarding messages from an email client (thinks MS Outlook) to a receiving email server

Explained here.

Lastly, to summarize, an email travelling would look something like this:

  • You hit send within your email client after composing the message, sending it to
  • The SMTP queries the DNS for records about
  • The DNS server fetches information about and sends it to the SMTP server
  • The SMTP server sends the email to someone’s mailbox at
  • The email goes through many SMTP servers before being relayed to the destination SMTP server
  • Upon reaching the destination SMTP server your email is forwarded and waits in the local POP3/IMAP server waiting on someone
  • Someone logs in to their email clients
  • Their email client queries the local POP3/IMAP server for new emails
  • Your email is copied (IMAP) or downloaded (POP3) to someone’s email client

This is nicely explained here, where you can also find the diagram shown below.

Here you can read more about these three protocols.

Default (un)encrypted ports for these protocols are:

POP3 – (110)995

IMAP – (143)993

SMTP – (25)587/465


Okay, so I talked a bit about phishing, how scary (real) it is, how an email travels, and I mentioned the variants of phishing attacks.

Before concluding, I’d like to emphasize again how important it is to understand/have some plan prepared against phishing as it is the best way attackers gain access, which in turn leads to some real ugly stuff. Prime example is ransomware, which is the most common way in which a ‘simple’ phishing attack evolves. (You can read more about it here, here, and here)

Finally, to let you go on a very dark note, please remember that phishing kits can be bought online quite easily, and that launching a phishing campaign can be done by someone less technical while the true danger remains; what comes after the attack i.e., what was it used for.  They might be less effective, true, but it is scary to think that it can be done in that way with so little effort – in comparison to the impact the attack can have.

Stay tuned for the next piece where I’ll be talking about header and body analysis, and more!

Cover by Mohamed Hassan

#phishing #smtp #pop3 #imap #vicarius_blog

As part of our mission to secure the world’s OT, IoT and Cyber Physical infrastructures, we invest resources into offensive research of vulnerabilities and attack techniques.

Ripple20 are 19 vulnerabilities revealed by Israeli firm JSOF that affect millions of OT and IOT devices. The vulnerabilities reside in a TCP/IP stack developed by Treck, Inc. The TCP/IP stack is widely used by manufacturers in the OT and IoT industries and thus affects a tremendous amount of devices.

Among the affected devices are Cisco Routers, HP Printers, Digi IoT devices, PLCs by Rockwell Automation and many more. Official advisories by companies who confirmed having affected devices can be found here, in the “More Information” section.

The most critical vulnerabilities are three that can cause a stable Remote Code Execution (CVE-2020-11896, CVE-2020-11897, CVE-2020-11901) and another that can cause the target device’s memory heap to be leaked (CVE-2020-11898).

On behalf of our customers, we set out to explore the real impact of these vulnerabilities, which we’re now sharing with the public.

The research has been conducted by researchers Maayan Fishelov and Dan Haim, and has been managed by SCADAfence’s Co-Founder and CTO, Ofer Shaked.

Exploitability Research
We set out to check the exploitability of these vulnerabilities, starting with CVE-2020-11898 (the heap memory leak vulnerability), one of the 19 published vulnerabilities.

We created a Python POC script that is based on JSOF official whitepaper for this vulnerability. According to JSOF, the implementation is very similar to CVE-2020-11896, which is an RCE vulnerability that is described in the whitepaper. Also mentioned about the RCE vulnerability: “Variants of this Issue can be triggered to cause a Denial of Service or a persistent Denial of Service, requiring a hard reset.”

Trial Results:
Test 1 target: Samsung ProXpress printer model SL-M4070FR firmware version V4.00.02.18 MAY-08-2017. This device is vulnerable according to the HP Advisory.

Test 1 result: The printer’s network crashed and required a hard reset to recover. We were unable to reproduce the heap memory leak as described, and this vulnerability would have been tagged as unauthenticated remote DoS instead, on this specific printer.

Test 2 target: HP printer model M130fw. This device is vulnerable according to the HP Advisory.

Test 2 result: Although reported as vulnerable by the manufacturer, we were unable to reproduce the vulnerability, and we believe that this device isn’t affected by this vulnerability. We believe that’s because the IPinIP feature isn’t enabled on this printer, which we’ve verified with a specially crafted packet.

Test 3 target: Undisclosed at this stage due to disclosure guidelines. We will reveal this finding in the near future.

Test 3 result: We found an unreported vendor and device, on which we can use CVE-2020-11898 to remotely leak 368 bytes from the device’s heap, disclosing sensitive information. No patch is available for this device. Due to our strict policy of using Google’s Responsible Disclosure, we’ve reported this to the manufacturer, to allow them to make a patch available prior to the publication date.

Key Takeaways
We’ve confirmed the exploitability vulnerabilities on our IoT lab devices.

On the negative side: The vulnerabilities exist on additional products that are unknown to the public. Attackers are likely to use this information gap to attack networks.
On the positive side: Some devices that are reported as affected by the manufacturers are actually not affected, or are affected by other vulnerabilities. It might require attackers to tailor their exploits to specific products, increasing the cost of exploitation, and prevent them from using the vulnerability on products that are reported as vulnerable.

SCADAfence Research Recommendations
Check your asset inventory and vulnerability assessment solutions for unpatched products affected by Ripple20.
The SCADAfence Platform creates an asset inventory with product and software versions passively and actively, and allows you to manage your CVEs across all embedded and Windows devices.
Prioritize patching or other mitigation measures based on: Exposure to the internet, exposure to insecure networks (business LAN and others), criticality of the asset.
This prioritization can automatically be obtained from tools such as the SCADAfence Platform.
Detect exploitation based on network traffic analysis.
The SCADAfence Platform detects usage of these exploits in network activity by searching for patterns that indicate usage of this vulnerability in the TCP/IP communications.
If you have any questions or concerns about Ripple20, please contact us and we’ll be happy to assist you and share our knowledge with you or with your security experts.

About Version 2 Limited
Version 2 Limited is one of the most dynamic IT companies in Asia. The company develops and distributes IT products for Internet and IP-based networks, including communication systems, Internet software, security, network, and media products. Through an extensive network of channels, point of sales, resellers, and partnership companies, Version 2 Limited offers quality products and services which are highly acclaimed in the market. Its customers cover a wide spectrum which include Global 1000 enterprises, regional listed companies, public utilities, Government, a vast number of successful SMEs, and consumers in various Asian cities.

About SCADAfence
SCADAfence helps companies with large-scale operational technology (OT) networks embrace the benefits of industrial IoT by reducing cyber risks and mitigating operational threats. Our non-intrusive platform provides full coverage of large-scale networks, offering best-in-class detection accuracy, asset discovery and user experience. The platform seamlessly integrates OT security within existing security operations, bridging the IT/OT convergence gap. SCADAfence secures OT networks in manufacturing, building management and critical infrastructure industries. We deliver security and visibility for some of world’s most complex OT networks, including Europe’s largest manufacturing facility. With SCADAfence, companies can operate securely, reliably and efficiently as they go through the digital transformation journey.