News items for tag work - Koos van den Hout

2018-09-24 Windows 10 WiFi can't deal with password changes
The work laptop is now "upgraded" to Windows 10. I wasn't sure about it as I saw Windows 7 as less annoying but it's the corporate choice.

And after I changed the password for my eduroam wifi-account it just gives an error and does not connect to the wireless network. The obvious choice to show the option to enter a new password does not pop up (unlike Android which came with that suggestion right away). Even the "network troubleshooter" doesn't come with the source of the connection problem let alone the obvious solution.

The Windows 10 "solution" is to just forget the network and discover it again. I'm glad this isn't a network where I need special options and a certificate to log in.

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2018-08-17 Trying (and failing) to correlate security logs
Since activating sendmail authentication with secondary passwords I see a number of attempts to guess credentials to send mail via my system. This is not very surprising, given the constant attack levels on the wider Internet.

For work I am looking at log correlation and monitoring and with that in mind I noted that finding the right information from sendmail where and when the attempt came from is quite hard since there are several processes busy and it's hard to correlate the logging. The failed attempt is logged by saslauthd in /var/log/auth.log:
Aug 16 12:28:57 greenblatt saslauthd[32648]: pam_unix(smtp:auth): check pass; user unknown
Aug 16 12:28:57 greenblatt saslauthd[32648]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost=
Aug 16 12:28:59 greenblatt saslauthd[32648]: do_auth         : auth failure: [user=monster] [service=smtp] [realm=idefix.net] [mech=pam] [reason=PAM auth error]
Aug 16 12:29:00 greenblatt saslauthd[32649]: pam_unix(smtp:auth): check pass; user unknown
Aug 16 12:29:00 greenblatt saslauthd[32649]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost=
Aug 16 12:29:02 greenblatt saslauthd[32649]: do_auth         : auth failure: [user=monster] [service=smtp] [realm=] [mech=pam] [reason=PAM auth error]
This is probably related to this sendmail log information:
Aug 16 12:28:56 greenblatt sm-mta[20716]: STARTTLS=server, relay=62.82.128.182.static.user.indesat.com [62.82.128.182] (may be forged), version=TLSv1/SSLv3, verify=NO, cipher=DHE-RSA-AES256-SHA, bits=256/256
Aug 16 12:29:02 greenblatt sm-mta[20716]: w7GASspx020716: 62.82.128.182.static.user.indesat.com [62.82.128.182] (may be forged) did not issue MAIL/EXPN/VRFY/ETRN during connection to MSP-v6
But I can't be sure as there are multiple 'did not issue MAIL/EXPN/VRFY/ETRN' messages in the logs. So I can't build a fail2ban rule based on this.

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2017-03-10 Improving the Internet security one service at a time
At work we (indirectly) get the scanning results from Shadowserver which now includes open VNC servers which is yet another service we don't really want left open to the Internet in general. A few were found which are now actively chased after to get them firewalled/disabled.

I really like the concept of shadowserver. ISPs that want the information can get full overviews of insecure services and botnet activity on their network. A full overview of what shadowserver looks for can be found at The scannings will continue until the Internet improves - Shadowserver.

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2016-03-14 VirtualBox 5 host-only network looks too much like a bridging adapter
Ever since I upgraded VirtualBox to a version 5 on my work laptop I can't start virtual machines which want to use the VirtualBox host-only network. For some communication I'd like to use that host-only network. Diving deep into the possible reasons found me VirtualBox can't find host-only adapters on Windows 10 which tells:
Oh and please double check that when you go to "Network Connections" and open the Properties dialog of the "VirtualBox Host-Only Network" connection, you see "VirtualBox NDIS6 Bridged Networking Driver" in the "This connection uses the following items" list.
This is indeed the case on my work laptop, and the use of the NDIS6 driver is an upgrade compared to VirtualBox 4. But I know the windows policy at work includes "you cannot use bridged networking" so I think I found the reason.

So now the solution is to use the main NAT network device. I was using the host-only network for some communication between the virtual machine and the host system or other virtual machines which should not be influenced by the 'outside world'. Now I seem to be using NAT as a firewall for that, which is wrong.

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2015-08-18 I'm a CISSPĀ© now
After taking the course in April and doing the exam in June I am now a Certified Information Systems Security Professional. As part of my job in computer security it is good to have this knowledge, it really helps me understand things.

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2015-06-20 A fast-changing security world
At work I reviewed something about TLS security I wrote in May 2014 and noticed I had to make some serious adjustments for the May 2015 state. SSLv3 is no longer accepted, SHA1 is no longer an accepted hashing algorithm and other changes.

This week on the home server greenblatt I had two different impacts from the latest OpenSSL update: SSL communications with the Fritz!Box was failing and SSL in sendmail was failing, both due to the latest insights into the security of the Diffie-Hellman key exchange.

These insights are very very new: in April I did a course in the Certified Information Systems Security Professional (CISSP) common body of knowledge and I learned the default Diffie-Hellman parameters were safe. Now we learn to generate them for each individual system at the same strength as the private key. Knowledge of cryptographic quality ages fast at the moment.

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2014-09-22 (#)
So work made a laptop with the standard Windows 7 software image available to me and I noticed when I took it home it doesn't do any IPv6. Which is not what I want. Some searching found How to disable IPv6 or its components in Windows - Microsoft Support which has the right answers which were used by the people creating this software image. I changed the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters\DisabledComponents registry key to 0x01 so I don't get the Isatap/Teredo tunnels.

Interesting remark in that support article:
We do not recommend that you disable IPv6 or its components, or some Windows components may not function. Additionally, system startup will be delayed for 5 seconds if IPv6 is disabled.
I guess I'll have to find another way to disable the Isatap/Teredo tunnels to make the system boot faster. I want IPv6 to work when it's available native or not at all. Some aspects of the work network make things slow when tunneling protocols are tried. Which is probably the reason of disabling it in the first place.

Update 2014-10-01: It seems this setting gets reset somehow: I am at the Surfnet Relatiedagen 2014 and just noticed the laptop has no IPv6 on the network here, which surprised me. But a check of the settings showed no IPv6 addresses at all, not even link-local. A check on my Android phone shows globally routable IPv6 addresses.

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2014-09-03 (#)
I had an appointment today at a to me new address. I have an Android phone so I use the car navigation available from google. The 'Car' application has the (extra?) option to navigate to my next appointment, which made the fact the invitation had the right address information very useful. I used that and found the location fine. After I arrived people asked me if I had any trouble finding it since it is in a somewhat unusual location. I would have had more problems with a map!

HTC One Tip: How to use Car mode video explaining HTC Car mode and navigating to appointments.

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2014-07-25 (#)
A clear sign this week I am not a system administrator anymore: I had no easy answer to "where can we find some Torx screwdrivers to open the dishwasher".

Using contacts that were from when I was a system administrator helped find the right screwdrivers and the dishwasher was opened and repaired.

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2013-12-18 (#)
Using SSL should secure your services, but it needs to be configured correctly to avoid several attacks and keep the chances low that third parties can decrypt the traffic. With the SSL Server test from Qualys SSL Labs you can check the intimate details of your https SSL configuration.

And when you wonder what to use to improve your score when using Apache mod_ssl, here is a configuration snippet shared by the right people at Tilburg University:
SSLEngine on
SSLProtocol all -SSLv2
# advies Wessel Dankers kub
SSLHonorCipherOrder on
SSLCipherSuite ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-SHA384:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-SHA256:AES256-GCM-SHA384:AES256-SHA256:ECDHE-RSA-RC4-SHA:ECDHE-RSA-AES256-SHA:RC4-SHA:AES256-SHA:AES128-SHA:DES-CBC3-SHA

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IPv6 check

Running test...
, reachable as koos+website@idefix.net. PGP encrypted e-mail preferred. PGP key 5BA9 368B E6F3 34E4 local copy PGP key 5BA9 368B E6F3 34E4 via keyservers

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