Squidnutz/extractedtest · Datasets at Hugging Face

text stringlengths 0 152
"","Playback","hear-odd-noise",
"2019-03-04 02:31:39","2019-03-04 02:31:39","2019-03-04 02:31:42",
3,3,"ANSWERED","DOCUMENTATION","1551666699.4",""

Open it up in a spreadsheet and it’ll be lined up neatly.

Caveats
The CDR system in Asterisk works very well for fairly simple call scenarios. However,
as call scenarios get more complicated—involving calls to multiple parties, transfers,
parking, and other such features—the CDR system starts to fall short. Many users
report that the records do not show all the information that they expect. Many bug
fixes have been made to address some of the issues, but the cost of regressions or
changes in behavior when making changes in this area is very high, since these
records are used for billing.

364

\|

Chapter 21: System Monitoring and Logging

As a result, the Asterisk development team has become increasingly resistant to mak‐
ing additional changes to the CDR system. Instead, a new system, channel event log‐
ging (CEL), has been developed that is intended to help address logging of more
complex call scenarios. Bear in mind that call detail records are simpler and easier to
consume, though, so we still recommend using CDRs if they suit your needs.

Channel Event Logging
Channel event logging (CEL) provides a more flexible means of logging the details of
complex call scenarios. Instead of collapsing a call down to a single log entry, a series
of events are logged for the call. This provides a more accurate picture of what has
happened to the call, at the expense of a more complex log.

For more details on CEL, check out the Asterisk wiki.

Conclusion
Asterisk is very good at allowing you to keep track of many different facets of its
operation, from simple call detail records to full debugging of the running code. Take
a look in the source code directories, and you’ll find many more components than
we’ve had space to cover here. These various mechanisms will help you in your efforts
to manage your Asterisk PBX, and they represent one of the ways that Asterisk is
vastly superior to most (if not all) traditional PBXs.

Channel Event Logging

\|

365

CHAPTER 22
Security

We spend our time searching for security and hate it when we get it.

—John Steinbeck

Security for your Asterisk system is critical, especially if the system is exposed to the
internet. There is a lot of money to be made by attackers in exploiting systems to
make free phone calls. This chapter provides advice on how to provide stronger secu‐
rity for your VoIP deployment.

Scanning for Valid Accounts
If you expose your Asterisk system to the public internet, one of the things you will
almost certainly see is a scan for valid accounts. Example 22-1 contains log entries
from one of the authors’ production Asterisk systems.1 This scan began with checking
various common usernames, then later went on to scan for numbered accounts. It is
common for people to name SIP accounts the same as extensions on the PBX. This
scan takes advantage of that fact.

Use non-numeric usernames for your VoIP accounts to make them
harder to guess. For example, in this book we use the MAC address
of a SIP phone as its account name in Asterisk.

1 The real IP address has been replaced with 127.0.0.1 in the log entries.

367

Example 22-1. Log excerpts from account scanning

[Aug 22 15:17:15] NOTICE[25690] chan_sip.c: Registration from
'"123"<sip:123@127.0.0.1>' failed for '203.86.167.220:5061' - No matching peer
found
[Aug 22 15:17:15] NOTICE[25690] chan_sip.c: Registration from
'"1234"<sip:1234@127.0.0.1>' failed for '203.86.167.220:5061' - No matching peer
found
[Aug 22 15:17:15] NOTICE[25690] chan_sip.c: Registration from
'"12345"<sip:12345@127.0.0.1>' failed for '203.86.167.220:5061' - No matching peer
found

...

[Aug 22 15:17:17] NOTICE[25690] chan_sip.c: Registration from
'"100"<sip:100@127.0.0.1>' failed for '203.86.167.220:5061' - No matching peer found
[Aug 22 15:17:17] NOTICE[25690] chan_sip.c: Registration from
'"101"<sip:101@127.0.0.1>' failed for '203.86.167.220:5061' - No matching peer found

The logs on any system will be full of intrusion attempts. This is simply the nature of
connecting systems to the internet. In this chapter, we will discuss some of the ways
to configure your system so that it will have robust mechanisms to deal with these
things.

"","Playback","hear-odd-noise",

"2019-03-04 02:31:39","2019-03-04 02:31:39","2019-03-04 02:31:42",

3,3,"ANSWERED","DOCUMENTATION","1551666699.4",""

Open it up in a spreadsheet and it’ll be lined up neatly.

Caveats

The CDR system in Asterisk works very well for fairly simple call scenarios. However,

as call scenarios get more complicated—involving calls to multiple parties, transfers,

parking, and other such features—the CDR system starts to fall short. Many users

report that the records do not show all the information that they expect. Many bug

fixes have been made to address some of the issues, but the cost of regressions or

changes in behavior when making changes in this area is very high, since these

records are used for billing.

364

|

Chapter 21: System Monitoring and Logging

As a result, the Asterisk development team has become increasingly resistant to mak‐

ing additional changes to the CDR system. Instead, a new system, channel event log‐

ging (CEL), has been developed that is intended to help address logging of more

complex call scenarios. Bear in mind that call detail records are simpler and easier to

consume, though, so we still recommend using CDRs if they suit your needs.

Channel Event Logging

Channel event logging (CEL) provides a more flexible means of logging the details of

complex call scenarios. Instead of collapsing a call down to a single log entry, a series

of events are logged for the call. This provides a more accurate picture of what has

happened to the call, at the expense of a more complex log.

For more details on CEL, check out the Asterisk wiki.

Conclusion

Asterisk is very good at allowing you to keep track of many different facets of its

operation, from simple call detail records to full debugging of the running code. Take

a look in the source code directories, and you’ll find many more components than

we’ve had space to cover here. These various mechanisms will help you in your efforts

to manage your Asterisk PBX, and they represent one of the ways that Asterisk is

vastly superior to most (if not all) traditional PBXs.

Channel Event Logging

|

365

CHAPTER 22

Security

We spend our time searching for security and hate it when we get it.

—John Steinbeck

Security for your Asterisk system is critical, especially if the system is exposed to the

internet. There is a lot of money to be made by attackers in exploiting systems to

make free phone calls. This chapter provides advice on how to provide stronger secu‐

rity for your VoIP deployment.

Scanning for Valid Accounts

If you expose your Asterisk system to the public internet, one of the things you will

almost certainly see is a scan for valid accounts. Example 22-1 contains log entries

from one of the authors’ production Asterisk systems.1 This scan began with checking

various common usernames, then later went on to scan for numbered accounts. It is

common for people to name SIP accounts the same as extensions on the PBX. This

scan takes advantage of that fact.

Use non-numeric usernames for your VoIP accounts to make them

harder to guess. For example, in this book we use the MAC address

of a SIP phone as its account name in Asterisk.

1 The real IP address has been replaced with 127.0.0.1 in the log entries.

367

Example 22-1. Log excerpts from account scanning

[Aug 22 15:17:15] NOTICE[25690] chan_sip.c: Registration from

'"123"<sip:123@127.0.0.1>' failed for '203.86.167.220:5061' - No matching peer

found

[Aug 22 15:17:15] NOTICE[25690] chan_sip.c: Registration from

'"1234"<sip:1234@127.0.0.1>' failed for '203.86.167.220:5061' - No matching peer

found

[Aug 22 15:17:15] NOTICE[25690] chan_sip.c: Registration from

'"12345"<sip:12345@127.0.0.1>' failed for '203.86.167.220:5061' - No matching peer

found

...

[Aug 22 15:17:17] NOTICE[25690] chan_sip.c: Registration from

'"100"<sip:100@127.0.0.1>' failed for '203.86.167.220:5061' - No matching peer found

[Aug 22 15:17:17] NOTICE[25690] chan_sip.c: Registration from

'"101"<sip:101@127.0.0.1>' failed for '203.86.167.220:5061' - No matching peer found

The logs on any system will be full of intrusion attempts. This is simply the nature of

connecting systems to the internet. In this chapter, we will discuss some of the ways

to configure your system so that it will have robust mechanisms to deal with these

things.