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Sweet32

Published: 27 October 2022    Last Updated: 03 November 2022

Sweet32 describes a birthday attack on 64-bit block ciphers. This attack has been demonstrated against both 3DES and Blowfish, against both VPNs as well as HTTPS traffic. This attack allows an attacker who can perform an interception attack to decrypt small amounts of ciphertext, such as session tokens and other sensitive cookie values.

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Padding Oracle On Downgraded Legacy Encryption (POODLE)

Published: 25 October 2022    Last Updated: 03 November 2022

Padding Oracle On Downgraded Legacy Encryption (POODLE) is an attack against SSLv3.0. It exploits two aspects of SSLv3.0. The first aspect involves an attacker performing an interception attack and modify network traffic between a client and server, downgrading the connection to SSLv3.0. The second aspect is a padding oracle issue with block ciphers in cipher-block chaining mode in SSLv3.0 which allows an attacker to decrypt small amounts of ciphertext within messages, such as session tokens and confidential cookie values.

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CBC-mode Ciphers

Published: 25 October 2022    Last Updated: 03 November 2022

The use of Cipher Block Chaining (CBC) mode ciphers is “discouraged”. This term is used as these cipher suites have not been formally deprecated but have effectively been superseded. For example, later version of Transport Layer Security support more secure cipher mode options such as Galois/Counter Mode (GCM) ciphers. Additionally, CBC-mode ciphers have had a series of vulnerabilities such as Lucky13, Zombie POODLE, GOLDENDOODLE, 0-Length OpenSSL, and Sleeping POODLE.

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Lucky 13

Published: 25 October 2022    Last Updated: 03 November 2022

Lucky 13 is a padding oracle vulnerability against CBC-mode ciphers in TLS that utilises a timing side-channel. This issue is due to a flaw within the SSL/TLS specification and is not implementation specific, however implementations may be able to harden against exploitation of this issue and prevent exploitation by removing the timing side-channel.

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Browser Exploit Against SSL/TLS (BEAST)

Published: 21 October 2022    Last Updated: 03 November 2022

BEAST is an attack that exploits several weaknesses within Transport Layer Security (TLS) 1.0 and older SSL protocols when using a CBC-mode cipher. The flaw is not strictly within the Transport Layer Security protocol itself, but is instead a known issue with Cipher Block Chaining (CBC).

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Compression Ration Info-leak Made Easy (CRIME)

Published: 21 October 2022    Last Updated: 03 November 2022

Compression Ration Info-leak Made Easy (CRIME) is a vulnerability in the compression used in Secure Sockets Layer (SSL) and Transport Layer Security (TLS). It also affects Google’s HTTP-like protocol SPDY. It requires an attacker to perform an interception attack but if successful could allow for the decryption of session tokens and other sensitive cookie values. The attack was demonstrated as practical in 2012.

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Decrypting RSA with Obsolete and Weakened Encryption (DROWN)

Published: 21 October 2022    Last Updated: 03 November 2022

Decrypting RSA with Obsolete and Weakened Encryption (DROWN) is a vulnerability in servers that support Secure Sockets Layer (SSL) version 2.0. It is a form of cross-platform Bleichenbacher padding oracle attack and would allow an attacker that is able to perform an interception attack to decrypt intercepted TLS connections by making specially crafted connections to an SSLv2 server that uses the same private key.

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TLS/SSL Vulnerabilities

Published: 21 October 2022    Last Updated: 03 November 2022

Look, there's a whole bunch of vulnerabilities in Secure Sockets Layer (SSL) and Transport Layer Security (TLS) and it can be difficult to keep up with them all, even if they have fancy names and logos! So here's a quick summary of each for you.

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Return of Bleichenbacher’s Oracle Threat (ROBOT)

Published: 21 October 2022    Last Updated: 03 November 2022

Return of Bleichenbacher’s Oracle Threat (ROBOT) is a padding oracle vulnerability that allows an attacker to illegitimately perform RSA decryption and signing operations with the private key of a TLS server. The attack would allow an attacker to intercept communications and later decrypt them.

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Browser Reconnaissance & Exfiltration via Adaptive Compression of Hypertext (BREACH)

Published: 21 October 2022    Last Updated: 03 November 2022

Browser Reconnaissance & Exfiltration via Adaptive Compression of Hypertext (BREACH) is a vulnerability similar in nature to CRIME, but where CRIME affected TLS/SPDY compression, BREACH affects HTTP compression. Where an application supports HTTP compression, reflects user-input within response bodies, and includes confidential information in that body – such as a CRSF token, it may be affected by BREACH. This attack was demonstrated as practical in 2013.

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RC4 NOMORE

Published: 21 October 2022    Last Updated: 03 November 2022

An attack against RC4 was demonstrated in 2015. This attack affects the use of RC4 in several protocols, including within Transport Layer Security (TLS) used by web browsers and web applications but also within WPA-TKIP used by wireless networks. This weakness in RC4 when applied to TLS can allow an attacker to decrypt a small amount of repeated content, such as a session token or other sensitive cookie values.

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Factoring RSA Export Keys (FREAK)

Published: 21 October 2022    Last Updated: 03 November 2022

Factoring RSA Export Keys (FREAK) is an attack against “export ciphers suites” which are cipher suites that have intentionally limited security due to prior regulation within the United States. This regulation placed restrictions on the strength of encryption algorithms used in software for exportation. This attack was demonstrated in 2015 and can allow an attacker who is able to perform an interception attack against HTTPS traffic to decrypt message contents.

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What is Penetration Testing?

Published: 22 August 2021    Last Updated: 03 November 2022

Penetration Testing, often abbreviated to PenTesting, is a method of testing the security of a system through attempting to discover and actively exploit vulnerabilities within the system. It is amongst the most effective methods of determining the actual risk posed by a system. This is due to the fact that the risk of present vulnerabilities is not estimated but they are exploited to determine how much leverage they would offer an attacker.

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PrivEsc: Insecure Service Permissions

Published: 06 August 2021    Last Updated: 03 November 2022

I’ve written a few articles recently about methods of escalating privileges on Windows machines, such as through DLL Hijacking and Unquoted Service Paths, so here I’m continuing the series with Privilege Escalation through Insecure Service configurations. This one’s pretty simple issue really, generally speaking it’s simply a matter of altering the service so that it runs the executable and parameters you want it to, instead the default configuration allowing you to supply a command and privilege level for the execution. So you can simply run the add user command as local system and create your own local administrator account!

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PrivEsc: Unquoted Service Path

Published: 06 August 2021    Last Updated: 03 November 2022

One method for escalating permission from Local/Domain User to Local Administrator, is "Unquoted Service paths". In my experience finding unquoted service paths is a common occurrence, however actually being able to exploit them is not. In this article we'll explore how to find these issues and how to quickly determine if they're exploitable or not.

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Calculating Subnets and CIDR Quickly

Published: 06 August 2021    Last Updated: 03 November 2022

A friend of mine mentioned recently that he has to work out subnet masks in his head for an exam and commented in reality he’d just use a subnet calculator. Whilst this is probably true, there’s a quick trick that might help if you’re calculating subnets under duress. This isn’t a full write up and offers no real explanation of why it works, it’s just pointing out a trick you may have missed which might come in handy one day!

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Calculating the Details of Awkward Subnets

Published: 06 August 2021    Last Updated: 03 November 2022

I posted recently about calculating subnets and CIDR notation quickly, but I didn’t mention in that post host to quickly get the Network ID, first host and Broadcast address for a subnet given an awkward address. This is another easy trick that covers that!

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Custom Rules for John the Ripper

Published: 06 August 2021    Last Updated: 03 November 2022

Whilst Hashcat is often provable faster than John the Ripper, John is still my favourite. I find it simple to use, fast and the jumbo community patch (which I recommend highly) comes packed with hash types making it a versatile tool.

One of the features of these tools, which is often unknown or at least under appreciated is the ability to create custom “rules” for teaching the tool how to dynamically generate potential passwords. Since Microsoft implemented “Password Complexity” and this was enforced around the globe, user have made the jump from a password of: password, to the [sarcasm] much more secure [/sarcasm]: Password1.

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Linux PrivEsc: Abusing SUID

Published: 06 August 2021    Last Updated: 03 November 2022

Recently during a CTF I found a few users were unfamiliar with abusing setuid on executable on Linux systems for the purposes of privilege escalation. If an executable file on Linux has the “suid” bit set when a user executes a file it will execute with the owners permission level and not the executors permission level. Meaning if you find a file with this bit set, which is owned by a user with a higher privilege level than yourself you may be able to steal their permissions set.

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Windows Desktop Breakout

Published: 06 August 2021    Last Updated: 03 November 2022

Many organisations “lock-down” their desktop environments to reduce the impact that malicious staff members and compromised accounts can have on the overall domain security. Many desktop restrictions can slow down an attacker but it’s often possible to “break-out” of the restricted environment. Both assessing and securing these desktop environments can be tricky, so I’ll run you through how I assess them here, highlight some of the tricks and the methodology that I use with the intention that both breakers and defenders can get a better look at their options.

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PrivEsc: DLL Hijacking

Published: 06 August 2021    Last Updated: 03 November 2022

I posted earlier about Privilege Escalation through Unquoted Service Paths and how it’s now rare to be able to exploit this in the real world due to the protected nature of the C:\Program Files and C:\Windows directories. It’s still possible to exploit this vulnerability, but only when the service executable is installed outside of these protect directories which in my experience is rare. Writing that post though got me thinking about another method of privilege escalation which I think is a little more common to see – DLL Hijacking.

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An Introduction to Penetration Testing AWS

Published: 06 August 2021    Last Updated: 03 November 2022

When penetration testing Amazon Web Services (AWS) environments there are different perspectives the assessment could consider, some are very similar to external infrastructure/web application assessments and some are different.

I’ll separate the things that are the same from the things that are different to traditional penetration testing by considering the following types of cloud testing and then breaking each one down into the kinds of testing that could take place:

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Spoofing Packets and DNS Exfiltration

Published: 06 August 2021    Last Updated: 03 November 2022

Following a successful penetration test, you may have large amounts of data to exfiltrate from an environment specifically hardened to make it difficult to exfiltrate data. For example, the network might have a firewall that explicitly blocks common exfiltration methods – such as SSH, HTTPS, HTTP.

It is common that you can still exfiltrate data from these networks by using DNS. For example you could make a request to a domain name that you control where the subdomain contains some information to be exfiltrated. Such as sensitive-data-here.attacker.example.com. DNS is a recursive system, such that if you send this request to a local DNS server, it will forward it on and on until it reaches the authoritative server. If you control the authoritative server, you can simply read the sensitive data from the DNS logs.

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An Introduction to PenTesting Azure

Published: 06 August 2021    Last Updated: 03 November 2022

I recently wrote an introduction to PenTesting an AWS Environment. A sensible place to start given that I included that in Q1 of 2018 Amazon holds a 33% market share in cloud whereas Microsoft only holds 13%. However I did want to add a few notes that are specific to PenTesting within Azure environments here.

Many of the concepts are the same however, in my AWS article I broke the perspective a penetration tester could take of a cloud environment down into testing “on the cloud”, “in the cloud”, and “testing the cloud console.” That concept remains the same, which is:

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Preventing Windows Accounts Being Bruteforced

Published: 23 January 2021    Last Updated: 04 November 2022

In a previous article we discussed how bruteforcing Windows accounts is often easier than people expect. In this post - we'll cover some steps to harden these accounts.

The Observation Window

When configuring an account lockout threshold on a Domain another setting is suggested, the observation window. This setting effectively reduces the protection of the account lockout by setting a timer. For example, a lockout threshold of 5 and an observation window of 30 minutes has the impact of meaning that if an attacker attempts 5 incorrect passwords within 30 minutes the account will lock - but four passwords would not cause it to lock.

Therefore, an attacker could attempt 4 passwords every 30 minutes - or 192 per account per day, without locking any accounts.

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Fixing LLMNR and NetBIOS-NS Spoofing

Published: 21 January 2021    Last Updated: 03 November 2022

In our article LLMNR and NetBIOS-NS Spoofing with Responder we stepped you through how to exploit a very common issue on Windows networks. In this one, we’re going to cover how to fix it.

Link-Local Multicast Name Resolution (LLMNR) and NetBIOS-Name Service (NBT-NS) are name resolution protocols that are enabled by default on Windows machines. They’re both used as a fallback for DNS. If a machine requests a hostname, such as when attempting to connect to a file-share, and the DNS server doesn’t have an answer – either because the DNS server is temporarily unavailable or the hostname was incorrectly typed – then an LLMNR request will be sent, followed by an NBT request. LLMNR is a multicast protocol and NBT-NS is a broadcast protocol.

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Extracting Domain Hashes: VSSAdmin

Published: 19 October 2020    Last Updated: 03 November 2022

We covered extracting domain hashes with Mimikatz previously, but that's not always the best approach - for example where anti-virus is getting in the way. However there are other options for the same goal. This time around we'll take a look at using Vssadmin, a built-in Windows tool. VSSAdmin is the Volume Shadow Copy Administrative command-line tool and it can be used to take a copy of the NTDS.dit file - the file that contains the active directory domain hashes.

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Becoming a Penetration Tester

Published: 19 October 2020    Last Updated: 03 November 2022

Breaking into Penetration Testing can be a daunting career move; so in this article we talked about ways you can make your first move towards a career in this industry. To be clear, this isn't a definitive guide to the industry - it's just our opinion on what has worked for our team and what we like to look for when hiring. So, when interviewing for a position as a junior penetration tester - what makes you stand out from the crowd?

Whilst it's certainly useful to know how to use common security testing tools, it's better if you can understand what's going on under the hood. It's also just as important to know how to remediate the issues found. For example, knowing which flags to use when executing Responder is good; but it's better if you can talk about the underlying protocols such as Link Local Multicast Name Resolution and why it can lead to significant vulnerabilities.

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LLMNR and NetBIOS-NS Spoofing with Responder

Published: 19 October 2020    Last Updated: 03 November 2022

Link-Local Multicast Name Resolution (LLMNR) and NetBIOS-Name Service (NBT-NS) are name resolution protocols that are enabled by default on Windows machines. They’re both used as a fallback for DNS. If a machine requests a hostname, such as when attempting to connect to a file-share, and the DNS server doesn’t have an answer – either because the DNS server is temporarily unavailable or the hostname was incorrectly typed – then an LLMNR request will be sent, followed by an NBT request. LLMNR is a multicast protocol and NBT-NS is a broadcast protocol.

Therefore, an attack can take place where an attacker responds to these requests with illegitimate requests. For example, directing the requesting user to connect to the attacker's machine where an authentication attempt will be made – disclosing hashed credentials for the targeted user.

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PrivEsc: Extracting Passwords with Mimikatz

Published: 19 October 2020    Last Updated: 03 November 2022

We recently published an article on using Incognito for privilege escalation as part of a short series on using Metasploit. In this article we’ll cover an alternative approach for privilege escalation – extracting plaintext credentials. Whilst incognito is generally easier to use, Mimikatz is powerful and flexible.

In this part we’re just going to look at password extraction; but Mimikatz can be used for many other attacks – such as extracting domain hashes from a domain controller. As before, password extraction is really a post-exploitation steps and is very useful for escalating from local administrator access to domain administrator access. As this is a post-exploitation step, we’ll be starting with a SYSTEM shell through PsExec for this demonstration. As an example of when these steps could be deployed, they could be a step taken after successfully performing an attack to gain an initial foothold such as LLMNR and NBT-NS Spoofing, which we covered previously.

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PrivEsc: Token Impersonation with Incognito

Published: 19 October 2020    Last Updated: 03 November 2022

Incognito is a tool which can be used for privilege escalation, typically from Local Administrator to Domain Administrator. It achieves this by allowing for token impersonation. As a local administrator can read the entirety of memory, if a domain administrator is logged in their authentication token can be stolen. We'll investigate its use here.

There are several types of authentication token on Windows systems, but Delegation tokens can be used network wide. This therefore allows an attacker to extract one of these tokens and then execute commands on other machines (such as the Domain Controller). Incognito can be executed within Meterpreter, or as a standalone EXE.

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Using Metasploit

Published: 19 October 2020    Last Updated: 03 November 2022

Metasploit is an exploitation framework. It’s a core tool of the penetration tester’s toolset and we use it for several of our vulnerability demonstrations, so it makes sense to write a quick “introduction to” for Metasploit. We’re going to look at the module system, navigating around, setting variables and running payloads.

Since there are so many modules, it's worthwhile becoming familiar with the search functionality. You can search for modules using the "search" command, and you can filter results based on features such as module type, CVE number, or platform. The command "help search" will reveal all filter options.

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Network Mapping with Nmap

Published: 19 October 2020    Last Updated: 03 November 2022

Before being able to determine if systems are vulnerable, it’s critical to first find as many active systems within the scope as possible and to accurately determine what services those systems expose. A common tool for use in network mapping is Nmap.

Before we start looking at the many, many, options that Nmap has, we'll take a look at a simple example. Nmap can be invoked with a target IP address and it will perform a default scan. If Nmap is invoked with administrative/root privileges it will perform a "half-open" SYN scan which is beneficial for its potential to be stealthier and faster than a "full" scan. A full-handshake scan can will be performed if administrative permissions are not granted, or optionally with the -sT flag.

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ASREP Roasting

Published: 19 October 2020    Last Updated: 03 November 2022

If an Active Directory user has pre-authentication disabled, a vulnerability is exposed which can allow an attacker to perform an offline bruteforce attack against that user’s password.

This attack is commonly known as “AS-REP Roasting” in reference to Authentication Service Requests, a part of the process of authentication with Kerberos. An attacker who is able to find a user with pre-authentication disabled can request an AS-REP ticket for that user and this will contain data encrypted with the user’s password.

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Bruteforcing Kerberos

Published: 19 October 2020    Last Updated: 03 November 2022

It is possible to brute-force Windows accounts directly, using tools like Metasploit using modules such as smb_login, which will target port 445 (SMB). However, it’s also possible to brute-force the Active Director authentication protocol Kerberos directly.

This can be beneficial to an attack for two reasons, the first is that it will be logged differently and depending on how the blue team are monitoring for attacks it might fly under the radar. A standard login attempt that fails will result in event 4625, whereas a failed Kerberos login attempt will likely result in event 4771.

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Kerberoasting

Published: 19 October 2020    Last Updated: 03 November 2022

Any domain user within Active Directory can request a service ticket (TGS) for any service that has an SPN (Service Principal Name). A part of the service ticket will be encrypted with the NTLM hash of the target user, allowing for an offline bruteforce attack.

This is true for user accounts and computer accounts, but computer account passwords are randomised by default and rotated frequently (every 30 days). However service user accounts may have weak passwords set which could be cracked. This attack is commonly called Kerberoasting. Although, don’t confuse this attack with the similarly named ASREP Roasting. A common setup where you might find this vulnerability is where a service account has been set up for Microsoft SQL Server.

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An Introduction to IPv6

Published: 19 October 2020    Last Updated: 03 November 2022

IPv6 is not new, RFC1883 discussed the protocol back in 1995. However, it has been updated several times, becoming a Draft Standard with RFC2460 in 1998, and an Internet Standard with RFC8200 in 2017!

If you’re wondering if there was an IPv5 the answer is sort of, in the Experimental Internet Stream Protocol, Version 2 (ST-II) which used the IP version number 5 within its packet header, that’s RFC1190. IPv7 was sort of RFC1475, IPv8 was sort of RFC1162, and for an April fools joke we go IPv9 in RFC1606.

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Bruteforcing Windows Accounts

Published: 19 October 2020    Last Updated: 03 November 2022

A common configuration on Windows Active Directory accounts is to have an account lockout threshold of say, 5 invalid attempts, and an observation window of 30 minutes. This is likely due to the fact that the “Suggested Setting” after setting a threshold is to enable a short observation window.

When setting an account lockout threshold, Windows “suggests” that you set the observation window at the same time, to 30 minutes. The observation window is often overlooked as a security risk; however it allows an attacker to perform a bruteforce attack without locking an account.

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Hashcracking with AWS

Published: 19 October 2020    Last Updated: 03 November 2022

Password cracking is a common step during compromising networks, from cracking wireless networks to compromising user passwords captured when LLMNR spoofing. In a previous post, I showed the steps to capture a WPA handshake and crack it using Hashcat. On my tiny travel laptop I achieved 416 hashes per second, which is…slow. AWS offers “GPU Optimized” EC2 instances which can offer a significant speed increase. 

In this post we'll run through setting up Hashcat on an AWS instance to allow for rapid password cracking. These instances are pricey, but you often only need to run them for short bursts.

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Extracting Domain Hashes: Mimikatz

Published: 14 October 2020    Last Updated: 03 November 2022

We previously covered how to perform incredibly fast hashcracking with AWS. In this post we’ll take a step back, and look at one simple method to extract the hashes from a domain controller. To be clear, this is a post exploitation step and to perform these steps a domain administrator account will be needed.

There are several tools which can be used to extract hashes directly on a domain controller, such as fgdump or Meteterpreter’s hashdump too. However, Mimikatz can perform this step from any domain joined machine, which is a little easier and often a benefit when it comes to antivirus evasion steps.

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