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Recently, dark matter indirect searches have gained a lot of attention,mostly due to the possibility of recent anomalies in cosmic rays and microwavesky maps being due to the annihilation or decay of dark matter. In this thesis,we argue however that these signals are plagued by irreducible astrophysicalbackgrounds and show how plausible conventional physics can mimic the allegeddark matter signals. In particular, we consider the possibility that the risein the positron fraction observed by the PAMELA satellite is due to theproduction through (hadronic) cosmic ray spallation and subsequent accelerationof positrons, in the same sources as the primary cosmic rays. We present a newanalytical estimate of the range of possible fluctuations in the high energyelectron flux due to the discreteness of plausible cosmic ray sources. Fittingour result for the total electron-positron flux measured by the Fermi satelliteallows us to fix the only free parameter of the model and make an independentprediction for the positron fraction. This model can be tested by consideringsimilar effects expected for nuclear secondary-to-primary ratios such as B/C. Arise predicted above O(100) GeV/n would be an unique confirmation of ourexplanation for a rising positron fraction and rule out the dark matterexplanation. Furthermore, we review the assumptions made in the extraction ofthe `WMAP haze' which has also been claimed to be due to electrons andpositrons from dark matter annihilation in the Galactic centre region. We arguethat the energy-dependence of their diffusion makes the extraction of the hazethrough template fitting unreliable. The systematic effects introduced by thiscan, under specific circumstances, reproduce the residual, suggesting that the`haze' may be just an artefact of the template subtraction.

Cosmic ray backgrounds for dark matter indirect detection