Category Archives: Security

Some information about the virus encryptor Trojan.Encoder.12544 attacked 06/27/2017

06/27/2017 After lunch, I received a call from one organization and reported that many computers stopped working, but some worked, I understood that Windows auto-update was enabled and all updates were installed, including the critical vulnerability fix that the virus uses – Microsoft Security Bulletin MS17-010 – Critical

On some infected computers, there was the following window (infected MBR area):

On the other side, the disk was checked for errors via CHDISK, as it turned out to be the second stage of the virus – disk encryption using AES-128-CBC algorithms and in this case, an immediate shutdown is necessary to recover the remaining unencrypted data.
Through special utilities, you could see only a few unencrypted data that can be recovered, and the rest can only be returned from backup copies made by system administrators since the decryptor is not available at the moment.
Under the old version of the virus last year, the decryptor was written https://github.com/leo-stone/hack-petya

The mail that was specified for requesting the decryption key was blocked after some time after the virus appeared, even about 45 transactions were received on the wallet.

Disabling ecryptfs encryption at home directory

It took one day to disable the ecryptfs encryption of the home directory, which was once set up when installing the system.

First of all, we make a copy of the home directory of the right user:

sudo cp -rp /home/user /home/user_backup

Get the mount point in the directory:

PRIVATE=`cat ~/.ecryptfs/Private.mnt 2>/dev/null || echo $HOME/Private`

Unmount the directory:

ecryptfs-umount-private

Install the rights to the directory:

chmod 750 $PRIVATE

Delete the directory and directories ~/.Private, ~/.ecryptfs:

rm -rf $PRIVATE ~/.Private ~/.ecryptfs

And also in the made copy:

rm -rf /home/user_backup/.Private /home/user_backup/.ecryptfs

If ecryptfs is no longer used in the system, then we will delete the utilities:

sudo apt-get remove ecryptfs-utils libecryptfs0

Install the right user directory:

sudo chmod 750 /home/user
sudo chown user:user -R /home/user

Copy the necessary files from the backup copy of the home directory.

Done.

You can see the built-in statement with the command:

ecryptfs-setup-private --undo

See also:
The solution to the error “Could not chdir to home directory /home/user: Permission denied”

nice and ionice. Process Priorities

nice – allows you to specify the priority of the processor performing various tasks, the range of priorities is -20 to 19, where 19 is the smallest, if not specified, then there will be a standard priority of 0. Convenient for example when packing data into archives so that this task does not load the server or when many processes need to be started, distributing the load, which occupy all CPU time.

Example of the execution of the command with the lowest priority:

nice -n 19 COMMAND

See the table of processes and their priorities as follows (column NI):

ps axl
ps -l

If the table is large, you can redirect the output of the command to Less and look at the page:

ps axl | less

To change the priority:

renice -n 19 PROCESS(PID)

Checking the default priority value (standard 0):

nice

ionice – allows you to specify the priority for I/O operations, for example, to reduce the load on the disk. The first class is from 1 to 3, then the priority is from 0 to 7, where 7 is the smallest.
There are three classes:
1) Real time – Preemptive without paying attention to other processes, indicating priorities from 0 to 7.
2) Best Effort — Standard with priorities from 0 to 7.
3) Idle — With idle time without priority.

Example of executing the command with the lowest I/O priority:

ionice -c2 -n7 COMMAND

To change the priority:

ionice -c2 -n7 -p PROCESS(PID)

To view the set priority:

ionice -p PROCESS(PID)

You can specify priorities at the same time via nice and ionice:

nice -n 19 ionice -c2 -n7 COMMAND

To specify high priorities, for example, you might need root permissions, this command should be executed as root user or added before the sudo command.

Solving the SSL problem “Connection is not secure – Parts of this page are not secure (such as images)”

I noticed once one site with a signed SSL certificate, a message from the Mozilla Firefox browser:

Connection is not secure – Parts of this page are not secure (such as images)

As it turned out, images from other sources were inserted on the site, so the connection can be considered not protected, and to solve this problem, you need to upload images to the current site and change the link on the pages, necessarily starting with https://.

If the site works on http:// and https://, and the pictures are on it, then the links should be changed for example from:

<img src="http://www.ixnfo.com/img.jpg">

to

<img src="/img.jpg">

Done.

The reboot script of Wi-Fi routers TP-Link

Below is an example of the TP-Link router reboot script, I will test it on TL-WR720N 2.0 from Ubuntu Server.

#!/bin/sh
ROUTER_IP="192.168.24.174"
USERNAME="admin"
PASSWORD="admin"

# exit if router is down
ping -q -c 1 "$ROUTER_IP" > /dev/null || exit

curl --basic --user "$USERNAME:$PASSWORD" -A "Mozilla/4.73 [en] (X11; U; Linux 2.2.15 i686)" --refer "http://$ROUTER_IP" "$ROUTER_IP/userRpm/SysRebootRpm.htm?Reboot=reboot"

The contents of the script will be placed in a new file, for example, using the nano editor (“CTRL+X” to exit and “y” to save the changes):

nano file.sh

And make it executable:

chmod 777 file.sh

After this, we execute:

./file.sh

Similarly, you can perform other functions instead of rebooting.