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Published on Leave a comment on Snort DGA Rule with Chrome

I had to investigate this Snort alert (3:31738):

PROTOCOL-DNS domain not found containing random-looking hostname - possible DGA detected

DGA here means "domain generation algorithm" – malware will often find its command and control servers using dynamically-generated domain names. It makes it harder for an infected victim to sinkhole the domains, and a malware author can spin up new ones according to the algorithm as necessary.

The DNS requests causing the alerts looked innocuous to me. It turns out that Chrome purposely issues invalid DNS requests every time it starts in order to root out malicious DNS servers. Discussed here:

https://isc.sans.edu/forums/diary/10312

These invalid requests occur independently of Chrome's prefetching behavior. This is a good Snort rule but it might be incompatible with Chrome.

Published on Leave a comment on Apache Logs in AWS

I recently started using CloudWatch, Amazon's host monitoring service. It has a number of features but I just wanted a way to view all my logs in one place. Configuring hosts to use CloudWatch was easy, and I described the process in an article on setting up Anonymous FTP.

Timeout Errors

With monitoring in place, I noticed a lot of 408 errors coming from the Apache logs on my WordPress instance. The errors appeared in:

/var/log/httpd/access_log
/var/log/httpd/ssl_access_log

...continue reading "Apache Logs in AWS"

Published on Leave a comment on NVIDIA Drivers on Ubuntu

I'm using a desktop that I got from System76 with an NVIDIA graphics card. Installing the NVIDIA drivers on Ubuntu wasn't simple, so here are the steps that I've gotten to work across multiple installations.

First remove any existing NVIDIA packages:

sudo apt-get remove --purge nvidia*
sudo apt-get autoremove

Next blacklist the nouveau driver. Without this step, the driver can re-appear after an update and cause problems. Create the blacklist file:

sudo vi /etc/modprobe.d/blacklist-nouveau.conf

And add the following lines:

...continue reading "NVIDIA Drivers on Ubuntu"

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Published on 1 Comment on Hosting Anonymous FTP

I wanted to create an FTP server to share some of the media that I've saved over the years. I like the old protocols and services and I plan to stand up more of them. Because each service has its own inherent security issues, the deployment process becomes an exercise in mitigating the risks. Check it out at ftp.disloops.com

I used an Ubuntu Server 14.04 LTS instance for the FTP server and gave it an AWS Elastic IP (EIP). An entry must be added to the /etc/hosts file when deploying Ubuntu instances in AWS:

127.0.0.1  (hostname here)

Without specifying the hostname, using sudo creates an error message. Next I ran updates and changed SSH to a non-default port, then installed VSFTPD and backed up the config file:

sudo apt-get update
sudo apt-get dist-upgrade
sudo vi /etc/ssh/sshd_config
sudo apt-get install vsftpd
sudo cp /etc/vsftpd.conf /etc/vsftpd.conf.old

...continue reading "Hosting Anonymous FTP"

Published on Leave a comment on WordPress in AWS

This site is being hosted in Amazon Web Services (AWS). It relies on a number of cloud services, including RDS, S3, and CloudFront. The following are some of the steps that were required to set it up.

Provisioning a Server

Create an AWS account if you don't already have one and complete the steps listed in the Identity and Access Management (IAM) service. It's especially important to set up multi-factor authentication (MFA) for your account. You should have an IAM user in the "Administrators" group when you're done.

Next go to the EC2 service, Amazon's storefront for virtual machines. Before launching a new instance, we'll create a key pair than can be used to access it securely. Use the following command locally to create a key pair:

ssh-keygen -t rsa -b 4096

Upload the public key by clicking "Key Pairs" and then "Import Key Pair" from the EC2 dashboard. Now we can launch an instance.

...continue reading "WordPress in AWS"

Published on Leave a comment on Secure Ubuntu 14.04 Configuration

I'm still using Ubuntu as my preferred Linux distro on personal machines. These are some of the settings that I configure each time I have to install it. Starting from the beginning:

Installation

Download the ISO image for the latest Long-Term Support (LTS) version and burn it to a disc. Boot from the disc to reach the installation menus and configure according to your needs. My own preference:

  • Plan to erase the entire disc to install Ubuntu
  • Do not download updates during installation
  • Do not encrypt the OS or home directory
  • Do not use Logical Volume Management (LVM)
  • Most importantly:
  • Do not allow automatic login
  • Do not allow login without a password

...continue reading "Secure Ubuntu 14.04 Configuration"