Backscattered light at wavelengths near the incident laser frequency of 0.35 μm irradiated 0.4 μm thick gold targets has been spectrally and temporally resolved. At the start of the laser pulse, the wavelength of the backscattered light is longer than that of the incident laser, and the wavelength subsequently increases with time. The observed scaling of the backscatter level with the incident laser intensity, the bandwidth of the backscatter spectrum, and the absolute value of the backscatter flux, are adequately described by absolute growth of the stimulated Brillouin scatter instability from thermal noise, provided that realistic hot spots in the incident laser profile are taken into account. The differences between backscattered light from high-Z and low-Z targets are discussed.