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This is a personal blog of 0xCardinal. I write about Information Security, Learnings, CTF WriteUps, etc.

Zone Identifier Blog Cover Image

Zone Identifier - Is your file downloaded from the internet?

Have you ever wondered, why your file is not working after downloading it from the internet? How does system know if the file is downloaded from the internet? The answers to this is Zone.Identifiers. What are Zone Identifiers? Zone Identifiers is an alternate data stream that points, from where the file came on the users' computer. Note: Alternate Data Streams are included with files on WIndows. This is typically the case with downloaded and blocked files....

October 6, 2022 · 2 min · Kumar Ashwin
DKIM Cover

Understanding DKIM - Email Security Series

DKIM is a technological advancement in the field of email security. SPF prevents non-authorized servers from sending emails, but it does not prevent all attempts at spoofing. This is where our next level of security comes into play. DKIM or Domain Keys Identified Mail aids to the security of the email as it adds a digital signature to every outgoing message, allowing receiving servers to verify that the message came from your organization....

July 26, 2022 · 4 min · Kumar Ashwin
SPF Cover

Understanding SPF - Email Security Series

Sender Policy Framework or SPF is an email authentication platform. It helps in specifying who is allowed to send emails from your domain. Making it harder for fraudsters to spoof sender information. RFC 7208 - https://datatracker.ietf.org/doc/html/rfc7208 SPF Records are used to specify the origin of the email to the world. It can be considered as a public list that specifies where an email is sent from. How does SPF records look like?...

July 25, 2022 · 4 min · Kumar Ashwin
Linux Command Line References

Linux - Command Line Struggles

Configure Network Using ip Command in Ubuntu Server Temporary Method - $ ip a # to get the interface name after connecting LAN $ sudo ip a add dev <network-interface-name> $ ip link set dev <network-interface-name> up $ sudo ip route add default via Permanent Solution - Ref: https://netplan.io/examples/ $ vim /etc/netplan/00-installer-config.yaml network: version: 2 ethernets: enx1027f579a565: dhcp4: false addresses: [] nameservers: addresses: [,,] routes: - to: default via: 192....

July 4, 2022 · 2 min · Kumar Ashwin
gRPC Concepts Blog Cover Image

gRPC: We are not RESTing Anymore

gRPC is a framework which is being used to build scalable and fast APIs. The framework from which it derives most of its positives is from the protocol it uses - HTTP/2. Apart from HTTP/2, it uses protocol buffer (protobuf) for the communication. gRPC can be useful in circumstances like - large-scale microservices connections real-time communication Low power & low bandwidth systems Multi-language environments Why Should We Care? Let’s talk Benefits The use of HTTP/2 over the TLS end-to-end encryption connection in gRPC ensures API security....

July 2, 2022 · 5 min · Kumar Ashwin
XSS vs CSRF Blog Cover Image

How is XSS different from CSRF?

An interesting discussion, led me to realize this is one of the commonly discussed topic and I thought a blog post for it might be helpful for someone. Cross-site request forgery and Cross-site scripting are both client side attacks which performs action on behalf of users. Just some context here - Cross-site scripting (or XSS) allows an attacker to execute arbitrary JavaScript within the browser of a victim user....

June 28, 2022 · 4 min · Kumar Ashwin

Kubernetes Concept

I have been wanting to learn about kubernetes k8s since long, and create this blog series. Here we are finally started (thanks to null cloud security study group ), so without wasting too much time let’s get started. I am learning this having a security mindset, to find common misconfigurations and understand the development process to understand the mitigation. K8s is a container orchestrator. Before diving too much into the depth let’s see what orchestrators/orchestrations are....

January 17, 2022 · 5 min · Kumar Ashwin

Anonymous Challenge Write-Up: WinjaCTF c0c0n 2021

WinjaCTF at c0c0n [2021]: I developed an easy challenge - called “Anonymous” - the challenge was based upon browser forensics. TL;DR Intended Way - Download the zip > Extract it > Navigate the Linux directory structure > To find a directory called .config > google-chrome > Default > Open the History File in SQL Browser > Search for URLs and upon up the URL to get a file with the name - formatted like flag....

November 15, 2021 · 1 min · Kumar Ashwin