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Something about NACL and Security Groups- Cloud Security

NACL and Security Groups:

Archietctre:
1. Security Groups are attached with every EC2 instance.
2. NACLs are situarted at boundary level- at subnet bounadries.

Firewall type:
1. NACLs are Stateless firewalls- meaing they don't keep track of packest going in and out. Everytime a packet leaves a boundary, the NACL checks if this packet is going to be allwed or not, and every time a packet comes inside the boundary, it checks again if the packet is allowed to enter or not. As an analogy, NACL can be condidered as Passwport Control, which even if remebers you by face, will check for your visa and passport before letting you in.
2. Security groups are stateful firewalls- meaning they remember what packet left and do not check when they come back. They keep track of ecah packet going out and in. As an analogy, they can be considered as a security guard siitng at the front gate, who remenbers who went out and let him in.

Traffic:
1. As NACL is stateles, it makes the decision to let a pa…
Recent posts

Effective way of preventing malicious file upload

The below are all the prescribed best practices when deciding to upload a file in a web application. The below are list of implemented approaches:

A few points:

Extension whitelistng: Obvious and the first line of defense was to white listing of extensions. A simple but easily by-passable approach. Good to have this approach.File header type checking: This helps prevents the above bypass. Even if the request is captured and tampered to include a restricted file (say exe), the application will check the file header (the magic nos) of the file and reject it. Suppose an application only accepts .pdf files and expects %pdf header, but when we try uploading an exe which has a header MZ, the file will not be uploaded. In this case even though you try replacing the MZ with %pdf, the file will get uploaded but the resultant file would be treated as a pdf and not an exe, so becomes useless.Content type: The content type decides how to treat/ render this file once uploaded. The application rest…

Some smbrelay points

Points to remember to avoid confusion when doing smbrelay:

1. NTLM hashes are stored in SAM database and on DC it's on NTDS.dit database

2. Until recent the NTLM hashes were combination of LM hash 'before' the semicolon, 'after' is the NT hash. After Win Server 2008, it's abolished and only NT hash is stored.

3. NTLM v2/ Net-NTLMv2 has different format and is based on challenges/ response algo and user's NT hash. They are n/w authentication protocols.

4. Pass-the-hash (PTH) attacks are not possible with NTLM v2 hashes, but with NTLM hashes.

5. NTLM hashes can be dumped from memory using Mimikatz type of tools and we can use NT hashes for PTH attack

6. We can get NTLM v1/2 hashes using tools like Responder.

7. We don't have to crack the hashes we get from Responder, we can directly relay them to other machine.

8. SMB signing prevents this sort of attacks

9. Tools to relay: Multirelay.py or ntlmrelayx.py with Impacket library

Now steps:

1. Responder inte…

SecureString implementation best practices

As the brush with 2-tier apps continues, the usual recommendations to manage the memory from leakage is to overwrite it quickly once its use is over. Although, it does not prevents the leakage completely, it reduces the attack surface by a considerable extent. Fortunately, for .Net application there's a method called SecureString. This class allows you to keep string data encrypted in memory. But a few things to keep in mind. Liked the below points from a discussion from stackoverflow post: Do you know how many times I've seen such scenarios(answer is: many!):
1.A password appears in a log file accidentally. 2.A password is being shown at somewhere - once a GUI did show a command line of application that was being run, and the command line consisted of password. 3.Using memory profiler to profile software with your colleague. Colleague sees your password in memory. Sounds unreal? Not at all. 4.Some tools such as  RedGate software that could capture the "value" of local va…

How to join HackTheBox challenge

Hack The Box (https://www.hackthebox.eu/) is an excellent collection of vulnerable vms, which are online to test/ hack them to upgrade the hacking skills.

To join the HTB, you need to have an invite code which needs to be entered while signing up. This invite code is not something someone will forward you. You have to generate one using your hacking skills and enter it to register to the site.

'View source' will not work, so we use developer tools and carefully going through we find a file called:
/js/inviteapi.min.js

Now go the browser and type: https://www.hackthebox.eu/js/inviteapi.min.js whose contents can be pasted to an online JavaScript interpreter but does not give any result:
But we can see makeInviteCode, which seems interesting. Let's search this in the console for this code. Executing makeInviteCode() gives a we see a data which seems to be ROT13 encoded: Decoding it gives some instructions: We use CURL to fire the above request, to get another Base64 encoded …

Good case for avoiding sensitive information in url

Nothing extraordinary here, just an interesting case I came across today. This can be one of the examples we can give to app teams too.



Someone posted a link from well known forum about some discussions on my WhatsApp group today. Upon clicking, it opened in the browser, after a while it prompted me to post something then I noticed that it wasn’t my name. :D Instead it was addressing me as ‘Ronnie’.



We both were surprised and amused. Then I searched all my emails and WhatsApp chats to find that once, long time back Ronnie had posted a link from the same forum to me, which was very long and contained probably session information, token etc.



Now this would have happened in background:

·         The long link (URL), from Ronnie, contained session information/ token in the URL

·         The session token has been persistent and active for a pretty long duration (almost 6 months)

·         I clicked a new unrelated link today from another group and Ronnie’s session token was replayed, logging me…