A DAC may be used to digitally control the attenuation of a signal by connecting the signal to the DACs Voltage reference input. Most DACs only allow a positive reference voltage lower than the positive supply voltage, so one has to use a device called a multiplying DAC, such as the MX7521.
A circuit like this may be called a NCA (numerically controlled amplifier) or DCA (digitally controlled amplifier)
Some possible devices:
MX7520 - single 10bit dac @ NOK 32,-
MX7501 - single 12bit dac @ NOK 51,-
AD5414 - dual 12bit dac @ NOK 96,-
DAC8803 - quad 14bit dac @ NOK 211,-